Palaeontologia Electronica palaeo-electronica.org

New genus of primitive wombat (Vombatidae, Marsupialia) from Miocene deposits in the Riversleigh World Heritage Area (Queensland, Australia)

Philippa Brewer, Michael Archer, Suzanne J. Hand, and Richard Abel

ABSTRACT

A new genus of primitive wombat, described here, is the most complete early wombat found. Two partial maxillae, as well as isolated teeth, were found within the Riversleigh World Heritage Area in northwestern Queensland, Australia. Previous to this, only a single species of wombat (Rhizophascolonus crowcrofti) was known from deposits older than 10 Ma, despite an estimated divergence date of 40 Ma between wombats and their closest living relative, the koala. We performed a phylogenetic anal- ysis incorporating the new taxon and using dental, cranial and postcranial characters as well as multiple outgroups in order to control for the diverse specialisations of closely related families and the continuing problem of recognising homologies within these groups. The results indicate a sister relationship between the new taxon and R. crowcrofti relative to all other wombats. Based on detailed comparisons between the cheek teeth of wombats, we propose a model which explains the observed differences in cheek tooth form and function in this group. If this model is correct, it could be used to map morphology against diet, and potentially climate.

Brewer, Philippa. Department of Earth Sciences, Natural History Museum, London SW7 5BD. [email protected] Archer, Michael. School of Biological, Earth & Environmental Sciences, University of New South Wales, Sydney, 2052, New South Wales, Australia. [email protected] Hand, Suzanne. School of Biological, Earth & Environmental Sciences, University of New South Wales, Sydney 2052, New South Wales, Australia. [email protected] Abel, Richard. Faculty of Medicine, Department of Surgery & Cancer, Imperial College London, London SW7 2AZ, England. [email protected]

Keywords: new species; new genus; phylogeny; Marsupialia; Vombatidae; Australia

http://zoobank.org/65F19586-5DC7-4DC1-8599-C16743FF024D

PE Article Number: 18.1.9A Copyright: Palaeontological Association March 2015 Submission: 28 March 2014. Acceptance: 28 January 2015

Brewer, Philippa, Archer, Michael, Hand, Suzanne J., and Abel, Richard. 2015. New genus of primitive wombat (Vombatidae, Marsupialia) from Miocene deposits in the Riversleigh World Heritage Area (Queensland, Australia). Palaeontologia Electronica 18.1.9A: 1-40. palaeo-electronica.org/content/2015/1060-new-wombat-from-riversleigh BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH

INTRODUCTION Extant wombats are medium- to large-sized (20-200 kg; size categories 2-3 of Andrews et al., 1979, categories D-G of Hernández Fernández et al., 2006) marsupial herbivores endemic to Austra- lia. There are seven recognised genera, of which two are extant; the Common Wombat (Vombatus ursinus) and the Hairy-nosed Wombats (repre- sented by two species, Lasiorhinus latifrons and Lasiorhinus kreftii). All three of the extant species are burrowing grazers. All wombats are classified in the family Vombatidae and together with six extinct families make up the Infraorder Vombato- morphia (Aplin and Archer, 1987). The closest liv- ing relative of the wombat is the Koala (represented by a single extant species, Phascol- arctos cinereus). Koalas are classified in their own FIGURE 1. Map of Australia showing the location of family, Phascolarctidae, and together with the Miocene wombat fossil sites. Vombatomorphia comprise the Suborder Vombati- formes (Aplin and Archer, 1987). cene deposits, with the greatest diversity of wom- Despite an estimated divergence date bats being found in the Pliocene-Pleistocene. between the Phascolarctidae and the Vombatidae Because extant wombats are specialist grazers, it of 40 Ma (Beck, 2008), only a single monotypic can be hypothesised that their post-Miocene genus of wombat has been described from depos- increase in diversity is related to the spread of its older than 10 Ma. This taxon, Rhizophascolonus more open habitats and greater availability of crowcrofti, was described on the basis of a single graze. However, each of these taxa almost cer- isolated tooth from Lake Ngapakaldi, central Aus- tainly occupied slightly different niches, and the tralia (Figure 1; Stirton et al., 1967), although addi- picture is likely to be more complex. tional specimens have since been described This paper describes specimens of a new (Brewer et al., 2008). genus and species of primitive wombat from early Wombats are significant in being the only Aus- Miocene deposits within the Riversleigh World Her- tralian marsupial group to possess hypselodont itage Area in northwest Queensland (Figure 1). cheek teeth. Hypselodonty is the condition where The specimens comprise two partial maxillae and the teeth grow continuously throughout life. Hyp- isolated teeth, possibly representing as few as two sodonty (high-crowned molars) and hypselodonty individuals. Despite the small sample size, this new (also known as euhypsodonty; Mones, 1982) are taxon represents the most complete early wombat adaptations to high rates of tooth wear and have known. independently evolved in numerous groups. Exam- ples include the cheek teeth of bovids and lago- MATERIALS AND METHODS morphs, respectively. The evolution of hypselodonty in the Vombatidae is poorly docu- Phylogenetic Analysis mented owing to the paucity of fossil material. Of the eight vombatiform families, only vom- Despite this, the Vombatidae are potentially valu- batids and phascolarctids have extant representa- able indicators of changing environmental condi- tives. Interfamilial relationships within the tions in Australia during the Neogene (e.g., Myers Vombatiformes are contentious (Archer, 1984; et al., 2001). Marshall et al., 1990; Munson, 1992; Murray, 1998; The oldest known hypselodont wombat is Black et al., 2012). Accordingly, a phylogenetic Warendja encorensis from the late Miocene of Riv- analysis was performed in which a range of out- ersleigh (Figure 1; Brewer et al., 2007). This genus group taxa were selected (Peramelemorphia and is also found in Pleistocene deposits in South Aus- Didelphimorphia). The choice of outgroup taxa tralia and New South Wales (Flannery and Pledge, concurs with the interordinal relationships deter- 1987; Brewer, 2007), forming a ghost lineage mined by Beck (2008), constrained in some cases throughout the Pliocene. In addition to Warendja, by the availability of postcranial material for some six additional wombat genera are first found in Plio-

2 PALAEO-ELECTRONICA.ORG taxa. A relatively unspecialised representative of at the Museum Victoria; NMV P, palaeontology col- each of the eight vombatiform families was lection at the Museum Victoria, Melbourne; QM F, included in the analysis. A total of 16 taxa were palaeontology collection at the Queensland coded in the analysis. Museum, Brisbane; SAM M, zoology collection at The data set consisted of dental, cranial and the South Australian Museum, Adelaide; SAM P, postcranial characters taken from the literature and palaeontology collection at the South Australian personal observations. Where characters were Museum, Adelaide; AR, temporary number for taken from the literature, they were re-scored, palaeontology collection at the University of New where possible, for each of the taxa in the analysis South Wales, Sydney; UNSW Z, and UNSW J, in order to verify the results of others and to ensure zoology collection at the University of New South consistency. Some characters used by other Wales, Sydney. authors in their phylogenetic analyses were rejected from this analysis because they were SYSTEMATIC PALAEONTOLOGY found to be highly intraspecifically variable (e.g., Order DIPROTODONTIA Owen, 1866 presence of frontal-squamosal contact: Springer et Suborder VOMBATIFORMES Woodburne, 1984 al., 1997; Wroe et al., 1998; Horovitz and Sánchez- Family VOMBATIDAE Burnett, 1830 Villagra, 2003; Black et al., 2012), or they were not Genus NIMBAVOMBATUS gen. nov. parsimony-informative for any of the taxa exam- ined. zoobank.org/C832B075-FB33-4C41-B5DF-EA48888AA8D3 A total of 115 characters were used in the Etymology. ‘Nimba’ is the Waanyi (the local analysis of which 28 are of the type ordered (Wag- Aboriginal language of the Boodjamulla region) ner) and 87 are of the type unordered. The data word for ‘small’. ‘Vombatus’ means ‘wombat-like’. matrix was analysed using Paup 4.0b10 (Swofford, Diagnosis. As for the species diagnosis until addi- 2002) using PaupUp graphical interface (Calendini tional species are described. and Martin, 2005). The branch and bound search Nimbavombatus boodjamullensis sp. nov. option was utilised, using a mixture of ordered and Figures 2-5 unordered characters (Appendices 1, 2). Multistate characters were treated as polymorphisms. All zoobank.org/1D7CD6A8-DB90-4D89-9B2F-7306C2DFDAA5 characters were presumed to have equal weight. Etymology of Specific Name. Refers to the Accelerated transformation (ACCTRAN) and Waanyi (the local Aboriginal language of River- delayed transformation (DELTRAN) character- sleigh) word for the Riversleigh area (Boodjamu- state optimisation methods were employed. Boot- lla). strap support (50%) for clades was determined Holotype. QM F23774 (left maxilla with C1, P3 and using 10,000 replicates. M1-4) Paratypes. QM F23725 (left maxilla fragment with Terminology P3, M1-3 and partial alveolus of M4); QM F30339 Incisor, premolar and molar homology follows 1 (right M ); QM F23773 (left Mx); QM F51404 (left Flower (1867). The position of the molar/premolar M ). boundary follows Luckett (1993). Anatomical 1 Type Locality and Distribution. All of the speci- nomenclature follows Nomina Anatomica Veteri- mens described here are from the Riversleigh naria (Frewein et al., 1994) where possible. Excep- World Heritage Area, northwestern Queensland tions are given in Brewer (2007) and Brewer et al. (19° 02’, 138° 45’). The holotype is from Boid Site (2007) or follow terms within the body of the text. East on Godthelp Hill. The paratypes are from Premaxilla is used instead of incisive bone. Jugal is Creaser's Ramparts on Hal's Hill. Precise location used instead of zygomatic bone. Vombatid sys- details for these localities may be obtained on tematics follows Dawson (1981, 1983a, 1983b). application to the Queensland Museum, Brisbane, Higher level systematic nomenclature follows Aplin Australia. and Archer (1987). Faunal and chronostratigraphic Geology. Boid Site East and Creaser’s Ramparts terminology of the Riversleigh Oligo-Miocene Site are freshwater limestone deposits which form deposits follows Travouillon et al. (2006). part of more extensive Oligo-Miocene to Pleisto- Institutional Abbreviations cene limestone deposits within the Riversleigh World Heritage Area (Archer et al., 1989, 1997; AM F, palaeontology collection at the Australian Woodhead et al., 2014). Creaser (1997) suggested Museum, Sydney; NMV C, mammalogy collection that Creaser’s Ramparts Site formed from a fresh-

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FIGURE 2. An animation of type specimen QM F23774, reduced for web viewing, based on CT data. The specimen was scanned at the Natural History Museum, London using a Metris X-Tek HMX ST 225 system. Volumes were con- structed using CT PRO (Metris X-Tek, UK) and visualised using VG Studio Max 2.0 (Volume Graphics, Heidelberg, Germany).

water limestone pool in or at the edge of rainforest Specific Diagnosis. Small vombatid with M1 and that Boid Site East is a tufa deposit (Creaser, length c. 6-7.5 mm, molars are bunodont with stylar 1997). Arena (2004) classified both sites as cusps reduced to absent, cheek teeth possess vadose cave deposits that were deposited within roots (three upper molar roots and two lower molar Depositional Phase 2 (Travouillon et al., 2006). roots), molars have relatively small but broad Age. Boid Site East and Creaser’s Ramparts Site inflections in enamel height with enamel extending group with other sites at Riversleigh in Faunal up to 3 mm below the furcation between the roots Zone B (Travouillon et al., 2006; Black et al., 2012, on the lingual surface of the upper molars and buc- 2013). Faunal Zone B is estimated to be early Mio- cal surface of the lower molars (i.e., the trailing sur- cene in age based on biocorrelation and stage of face), but not extending onto the roots on other evolution arguments (Archer et al. 1989, 1997, surfaces, enamel is up to 0.5 mm thicker on the 1999). Radiometric dating of speleotherms from trailing surface of the molars relative to the other five Faunal Zone B deposits at Riversleigh pro- surfaces, C1 is present as is a posterior incisor (I3 duced dates between 16 and 19 Ma (Woodhead et and/or I2), the ventral root of the zygomatic arch is al., 2014). only 2.5 mm dorsal to the molar row and there is no infraorbital fossa.

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FIGURE 3. Left maxillary fragment of Nimbavombatus boodjamullensis from Boid Site East (QM F23774). Left panel (photographs) of 1, occlusal (ventral) view of tooth row and 2, buccal (lateral) view. Scale bar represents 10 mm. Right panel (line drawings) of 3, occlusal (ventral) view and 4, buccal (lateral) view. Grey shading represents enamel.

Description an anteroposterior ridge that crosses the premaxil- lomaxillary suture. This ridge is 4.2 mm medial to Description of the cranial bones is based on the interalveolar margin. On the dorsal surface of the holotype (QM F23774; Figures 2, 3) unless oth- the palate (within the nasal cavity) there is a corre- erwise specified. sponding ridge and sulcus extending posteromedi- Nasal Cavity. The nasopharyngeal meatus is oval ally from the incisive foramen. A minor foramen on in cross-section and wider (mediolaterally) than the ventral surface of the palate is located close to tall. The turbinals are preserved dorsal to the pos- the interalveolar margin and anterior to C1. terior moiety of M1 and posteriorly as far as the Palatine. The palatine forms part of the lateral wall ventral extent of the cribriform plate (a small por- of the cranium medial to the maxillary sulcus within tion of which is preserved). the orbital region. The dorsoventrally orientated Premaxilla. A 4.0 mm long sliver of the premaxilla palatolachrymal suture forms the anterior edge of is preserved anterior to the premaxillomaxillary the palatine on this wall. The ventral edge of the suture on the left palate. The posterior edge of an palatine is formed by the palatomaxillary suture. incisor alveolus forms the anterior tip of this sliver The latter is approximately coincident with the of bone. The premaxillomaxillary suture is approxi- maxillary sulcus and intersects the sphenopalatine 1 mately level with the anterior edge of C between foramen at the posterolateral edge of the sulcus. the median palatine suture and the anterolingual Posterior to this the palatomaxillary suture is orien- 1 tip of C on the ventral surface of the palate. The tated posterolaterally until it intersects the dorsal premaxillomaxillary suture intersects the posterior posterolateral palatine foramen at the maxillary edge of the left incisive foramen midway between tuber. The suture curves around the posterior sur- the canine and the median palatine suture. The lat- face of the maxillary tuber and intersects the ven- eral edge of the incisive foramen is emphasised by tral posterolateral foramen on the posteroventral

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FIGURE 4. Left maxillary fragment of Nimbavombatus boodjamullensis from Creaser’s Ramparts Site (QM F23725). Photographs of 1, occlusal (ventral) view, 2, buccal (lateral) view and 3, lingual (medial) view. Scale bar represents 10 mm. 4, Line drawing of occlusal (ventral) view. Grey shading represents enamel. Asterisk marks presence of distinc- tive wear facet on trailing edge enamel (see text for details). edge of the alveolar process. The suture is indis- lachrymojugal suture forms the medial edge of the tinct beyond this point. The dorsal and posterior jugal within the orbital region and is dorsoventral in edges of the palatine are not preserved. orientation. The jugal between the contact with the Jugal. Only the anteromedial portion of the jugal maxilla on the anterior wall of the orbit and the dor- bone is preserved. The lachrymojugal suture forms sal surface of the arch dips steeply posteroven- the medial edge of the jugal bone. The lateral-most trally. point on the suture is located on the tightly convex Lachrymal. The lachrymal is largely intact with dorsal surface of the zygomatic arch. The anterior only the medial edge missing. The preserved por- edge of the jugal is formed by the maxillojugal tion is subrectangular in dorsal view. The lachrymal suture, which curves laterally and posteroventrally contacts the maxilla at its anterior edge, anterome- down the anterior facial surface as far as the ven- dial to the zygomatic arch and along its lateral tral root of the zygomatic arch. This suture cuts edge within the orbit. The lateral edge of the lach- dorsomedially across the arch and onto the ante- rymal also contacts the jugal on the dorsal surface rior wall of the orbit where it is mediolaterally orien- of the zygomatic arch and on the anterior wall of tated almost as far as the lateral wall of the the orbit. The posterolateral tip of the lachrymal cranium (medial wall of the orbit). The jugal does abuts the medial wall of the maxillary sulcus 4 mm not contribute to the medial wall of the orbit. The posterior to the maxillary foramen. The posterior

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FIGURE 5. Isolated molars of Nimbavombatus boodjamullensis from Creaser’s Ramparts. 1, Right M1 (QM F30339). 2, Left M1 (QM F51404). 3, Left Mx (probably M2 or M3) (QM F23773). From left to right views are: buccal, lingual, anterior, posterior, stereo of occlusal surface and line drawing of occlusal surface. Scale bar for photographs rep- resents 10 mm. Grey shading on line drawings represents enamel. L indicates lingual side, B indicates buccal side. edge of the lachrymal forms part of the lateral wall The maxilla and jugal bones of the infraorbital of the cranium within the orbit and is bounded pos- region form a continuous ventrally and posterolat- teriorly by the palatine. However, the suture erally sloping facial surface. There is no infraorbital between these bones is not clearly defined. fossa or facial crest. The ventral surface of the The lachrymal foramen is anteromedially anterior root of the zygomatic arch is mildly convex located on the lachrymal bone in dorsal view. It is and forms an almost horizontal shelf in anterior medial to the zygomatic arch and on the anterome- view, 2-2.5 mm dorsal to the alveolar margin at M2. dial edge of the orbit. The foramen is 1.5 mm in The lateral surface of the maxilla is almost vertical diameter and approximately circular. Posterior to between M2 and the anterior root of the zygomatic this, the lachrymal is indented and forms a shallow arch. concavity approximately 4 mm in diameter on the The maxillojugal suture commences at its anteromedial wall of the orbit. The lachrymal canal anterodorsal contact with the lachrymal and extends anteromedially from the lachrymal fora- extends laterally and posteroventrally across the men to the nasal cavity. It opens into the latter at a facial surface as far as the anteroventral edge of small protuberance and continues as a groove the zygomatic arch. The suture is complex in ventral to the opening. cross-section with an overall dorsomedial inclina- Maxilla. The majority of the left maxilla is pre- tion between the anteroventral edge of the arch served, although the anterodorsal portion is miss- and the anterior wall of the orbit. The suture is ing, including the contact between the maxilla and mediolaterally orientated across the anterior wall of the premaxilla, nasal and frontal bones. the orbit and is 3.3 mm posteroventral to the dorsal surface of the arch at this point. It meets the lachry-

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mal, anterior to the position of the maxillary fora- rior edge of P3, and the posterior foramen is level men. The maxillojugal suture is deeply incised on with the anterior moiety of M2. the anterior surface of the orbit and marks the There is a large maxillary vacuity that is anterior extent of a shallowly sloping orbital floor. approximately rectangular in shape, with rounded The orbital floor slopes posteroventrally at an angle corners. The anterior edge of the vacuity is level of approximately 20º to the alveolar margin, ending with the posterior edge of M2. The posterior edge at the dorsal posterolateral palatine foramen, just of the vacuity is not preserved but appears to 4 posterior to M . extend to at least the anterior moiety of M4. The Between the alveolar process and the lateral mediolateral width of the left vacuity is approxi- wall of the cranium within the orbit is the maxillary mately 7.5 mm. The palate is 2.5 mm in mediolat- sulcus. The sulcus is deep and well-defined. It is eral width between the vacuity and the lingual 12 mm in length and slopes ventrally and postero- edges of the molars. The anterior part of a median medially. It commences at the maxillary foramen process is preserved. It is not clear whether the and finishes just posterior to the sphenopalatine process partially or wholly divided the maxillary foramen. The sphenopalatine foramen is ovate and vacuity. opens directly into the nasal cavity. Anterior and Medial and posterior to M4 on the palatal sur- posterior to the sphenopalatine foramen, within the face there is an elongated fossa that probably rep- maxillary sulcus, are minor foramina. The maxillary resents the ventral posterolateral palatine foramen. foramen is located 3.2 mm posterior to the maxillo- The palatomaxillary suture intersects the dorsal jugal suture. The maxillary foramen and sulcus posterolateral palatine foramen on the dorsal sur- form a deep incision in the maxilla, resulting in a face and curves around onto the ventral surface of shelf-like appearance of the anterior part of the the palate, intersecting this probable ventral open- floor of the orbit. The anterior orbital floor is later- ing of the posterolateral palatal foramen. ally continuous with the dorsal surface of the alveo- The palate is 16.3 mm in mediolateral width at lar process. M2 and is similarly wide along the length of the The anterior part of the maxilla on QM F23774 1 is broken along a posterodorsally-orientated break cheek tooth row. The palate narrows anterior to M that passes anterior to the infraorbital foramen and and is 9.3 mm in width between the median pala- meets the lachrymal anterior to the lachrymal fora- tine suture and the interalveolar margin, posterior men. The infraorbital foramen is located 6 mm dor- to the canine. The cheek tooth row is arcuate in ventral view (laterally convex). The buccal contact sal to the alveolar margin at P3. It is approximately between M2 and M3 forms the lateral-most point of 7.5 mm in diameter and generally circular in cross- 3 1 section. The opening of the foramen faces anteri- the arc. The diastema between P and C is 3.3 orly and slightly laterally. 1.5 mm posterior to the mm. The cheek tooth row is 30.7 mm long. The infraorbital foramen, the medial wall of the infraor- widest part of the tooth row is represented by the bital canal is perforated by the opening of the inci- anterior moieties of M2 and M3. sivomaxillary canal. Medial to this the numerous C1. C1 is preserved only on the left side of QM septa and vacuities of the alveolar canals are F23774 (Figures 2, 3). It is located on the premaxil- exposed in longitudinal section. The infraorbital lomaxillary suture, 3.3 mm anterior to P3 and 4.2 canal is 13 mm in length between the infraorbital mm posterior to the anterior edge of the specimen. foramen and the maxillary foramen. It is separated from both by a diastema. In occlusal On the lateral surface of the alveolar process, view it is ovate in cross-section. C1 is 4.2 mm in alveolar jugae increase in prominence anteriorly anteroposterior length and 3.5 mm in buccolingual and are particularly marked either side of the width measured at the alveolar margin. Length and canine. On the ventral surface of the palate on QM width constrict towards the crown apex. It is 2.4 F23774 there are a number of minor ridges and mm in anteroposterior length just below the apex. sulci located between the incisive foramen and the The posterior surface of the tooth is concave, and anterior edge of the maxillary vacuity. Ridges and the anterior surface is convex in lateral view. The sulci are not as obvious on the ventral surface of buccal and lingual surfaces are mildly convex. The QM F23725. However, two minor palatal foramina, posterior surface slopes posterobasally at an angle up to 1 mm in diameter, are present on the palatal of approximately 65° to the alveolar margin. The surface on the latter specimen. They are located dorsoventral height is 4.7 mm measured on the 4.5 mm medial to the lingual edge of the cheek buccal side between the alveolar margin and the teeth. The anterior foramen is level with the ante- crown apex.

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Enamel is restricted to the apical half to third extension of the dip in the crest between the of the crown. The enamel is largely restricted to the paracone and metacone. Between the paracone, buccal surface due to a large ovate wear facet on the lingual cusp and the paracone-metacone crest, the lingual surface which has penetrated the the occlusal surface is relatively flat and slopes enamel. The maximum enamel height on the buc- posterolingually towards the posterior basin. Wear cal surface is 2 mm. The lingual wear facet is 3 mm of this surface has breached the enamel on QM in height and 2.3 mm in anteroposterior width mea- F23725. A minor crest extends posterolingually sured at its widest point, 1.6 mm from the crown from the metacone. On QM F23774, there may be apex. The wear facet is relatively flat and faces a slight cingulum posterior to this posterolingual slightly posteriorly. Apically, the facet is mildly con- crest. The posterolingual crest partially encloses a cave and surrounded entirely by dentine. Basally, small posterior basin that is deepest immediately the facet is mildly convex and edged by enamel. In adjacent to the crest. buccal view, the apex of the crown slopes posteri- The long axis of the tooth (the anteroposterior orly slightly and is flat to mildly convex. In occlusal length) is continuous with the arc of the molar row. view the apical edge is convex buccally. The outline of the tooth in occlusal view is pinched P3. P3 is preserved on the left side on QM F23774 in (constricted) on the buccal side approximately and QM F23725 (Figures 2-4). In occlusal view the midway between the anterior and posterior edges tooth is subovate with the posterior half slightly of the tooth. The anterior quarter of the buccal sur- wider in buccolingual width than the anterior half. face is relatively flat to concave and faces antero- P3 leans posteriorly at an angle of 60° to the alveo- buccally in occlusal view. The posterior quarter lar margin on QM F23774. In contrast, on QM faces posterolingually. The lingual surface is con- F23725 it is more vertically orientated. P3 and M1 cave in occlusal view between the parastyle and contact on the buccal side in occlusal view. In buc- lingual cusp (lingual most point on the tooth). Pos- cal view the occlusal profile is continuous between terior to this, the lingual surface is also concave P3 and M1 on QM F23725, but is stepped on QM and faces posterolingually. There are two roots; anterior and posterior. F23774. There is a gap between P3 and M1 just The interradicular bifurcation appears to be above the alveolar margin. approximately level with the alveolar margin on The occlusal surface is dominated by the 3 paracone, which forms the highest point on this both P specimens. Both roots are approximately surface. It is located above the posterior half of the circular in shape (based on QM F23774; the roots anterior root. A crest extends posteriorly, basally on QM F23725 are slightly damaged) and of and slightly buccally away from the paracone approximately equal size. The anterior root on QM towards a smaller and lower cusp located near the F23774 is 2.8 mm in buccolingual width and posterior edge of the occlusal surface (the approximately 2.5 mm in anteroposterior length. metacone). The crest dips in height midway The posterior root QM F23774 is 3.5 mm in bucco- between these cusps and the occlusal surface lingual width and approximately 2.2 mm in antero- either side of this dip is concave. The paracone- posterior length. metacone crest is located buccal to the midline of Enamel height is greater on the buccal side the tooth. A crest also extends anterolingually and than on the lingual side. A thin tongue of enamel basally from the paracone. This latter crest termi- extends as far as the alveolar margin on the ante- nates in a small cusp on the anterolingual ‘corner’ rior half of the buccal surface on QM F23725. A of the occlusal surface (the parastyle) on QM similar tongue of enamel is not present on the pos- F23725. Either side of this steeply inclined crest, terior half of the tooth and the base of the enamel the enamel on the anterior and lingual faces of the is 1.5 mm above the alveolar margin at this latter tooth are slightly troughed. point. The base of the buccal enamel on QM A slight crest extends posterolingually from F23774 is obscured by cementum. On both QM the paracone towards a low cusp on the lingual F23725 and QM F23774 buccal enamel height is edge of the tooth on QM F23725. This lingual cusp greatest midway across the roots. On the anterior forms the most lingual point on the occlusal surface surface, the base of the enamel slopes basally and is located posterior to the midpoint between towards the lingual surface. The posterior surface 1 anterior and posterior edges of the tooth. A groove is obscured by M but enamel height on this sur- separates the lingual cusp from the posterolingual face appears to be quite small. On the lingual sur- crest of the paracone. Immediately posterior to the face, there is a significant decrease in enamel lingual cusp is another groove which is a lingual

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height between the anterior edge of the tooth and cone to the paracone and one on the posterior moi- the posterior third of the tooth. ety connecting metacone and metaconule. Upper molars. The upper molars are subrectangu- A transverse (buccolingual) valley connects lar in outline (in occlusal view) and mildly bilobed. the buccal and lingual constrictions. The trans- The occlusal surface is longer in anteroposterior verse valley is deepest near the midpoint between length than buccolingual width. Crown length the buccal and lingual constrictions. This is also the decreases slightly below the occlusal surface. deepest point on the occlusal surface. Between the Maximum length of the occlusal surface is located anterior margin of the tooth and the anterior loph is just lingual to the buccal margin. Anterior and pos- a basin. This anterior basin is mainly restricted to terior moieties are wider than long. The anterior the buccal half of the occlusal surface. A crest moiety is slightly larger than the posterior moiety in marks the anterior margin of the occlusal surface. anteroposterior length and buccolingual width, par- A low crest forms the posterobuccal margin of the ticularly towards the posterior of the molar row. The occlusal surface. The posterior s surface of the anterior moiety increases in width between the posterior loph dips steeply towards this low crest. occlusal surface and the alveolar margin due to the Occlusal wear is greatest on M1 and sloping lingual surface. In contrast, the posterior decreases posteriorly along the molar row. As moiety generally decreases in width between the such, the unworn crown morphology presented occlusal surface and the alveolar margin. These here is based mostly on M2-4. QM F23774 is less differences in width as a result of distance below worn than QM F23725. The occlusal surface on M1 the occlusal surface are greatest at the anterior of largely consists of dentine with most of the enamel the molar row. having been lost. The crown perimeter is, however, The widest part of the molar row is across the surrounded by enamel. Wear is greatest on cusp anterior moiety of M2 or M3. Adjacent molars con- apices and on the anterior and posterior lophs tact midway between their buccal and lingual mar- resulting in a ‘bow-tie’ pattern of wear on each moi- gins. Tooth height exposed above the alveoli is ety (Figures 3.3, 4.4). Wear is particularly concen- greatest on the lingual side relative to the buccal trated on the lingual half of the occlusal surface. side. Tooth height exposed above the alveoli The lingual margin is relatively flat in lingual view decreases posteriorly along the molar row. on M1-2 (M1-3 on QM F23725) and lower in height The constriction between the moieties is more relative to the buccal margin. pronounced on the lingual side in occlusal view. In Enamel height is greatest on the lingual sur- profile it is more pronounced on the buccal side face, particularly on the anterior moiety. Enamel with the lingual constriction wearing to a similar height decreases at the lingual constriction. There height as that of the anterior and posterior moi- is a slight increase in enamel height posterior to eties. The constriction is represented on the buccal the lingual constriction on the posterior moiety. surface by a vertical groove between the mildly Enamel height decreases onto anterior and poste- convex moieties. The constriction on the lingual rior surfaces from the lingual surface. On the buc- surface slopes posterobasally at an angle of 65 to cal surface, enamel height is greatest beneath the 85° to the occlusal surface. This angle generally paracone and metacone. Enamel height decreases increases between M2 and M4 (i.e., it approaches towards the anterior and posterior edges of the vertical on M4). The slope of the lingual surface tooth and at the buccal constriction. Enamel is either side of the constriction is shallower immedi- thickest (between 0.4 to 0.7 mm thick) on the lin- ately anterior to the constriction than posterior to it gual side. Enamel appears to increase slightly in on M1-3. Away from the occlusal surface, the lin- thickness between M1 and M3 on QM F23725. Ver- gual surface on the posterior moiety slopes slightly tical cracks in the enamel extend between the buccally. occlusal surface and the basal enamel-dentine The occlusal morphology is bunolophodont. junction (EDJ). There are a few small patches of There are four main cusps; one in each quadrant what appear to be cementum on the lingual (inferred to be the paracone, metacone, protocone enamel. There are grooves on the outer enamel and metaconule). All cusps are located at the mar- surface on the lingual side. These grooves are gin of the tooth crown. A medial crest slopes probably the remains of a complex cementum- basally from each cusp and meets the basally slop- enamel junction (CEJ). ing medial crest of the opposing cusp. There are There are three roots: an anterolingual root, thus two weakly developed buccolingual ‘lophs’: an anterobuccal root and a posterior root. The pos- one on the anterior moiety connecting the proto- terior root is buccolingually elongated so that it

10 PALAEO-ELECTRONICA.ORG extends across the entire width of the posterior rior to the constriction and approximately parallel to moiety. It has the widest buccolingual dimensions the buccal margin. of all three roots. The anterobuccal root is the The lingual surface near the occlusal surface smallest of the three roots in all dimensions, is shallowly inclined immediately anterior to the although it is similar in anteroposterior width to the constriction relative to the rest of the lingual sur- posterior root. In anterior view the anterobuccal face. In addition, the anterolingual root and the lin- root is located beneath the buccal half of the ante- gual surface directly occlusal to it project rior moiety, and the anterolingual root is located posterolingually (and basally) so that the root is beneath the lingual half of the anterior moiety. The almost directly lingual to the constriction at the anterolingual root is the largest of the three roots in alveolar margin. M1 tapers lingually slightly overall volume and is widest anteroposteriorly. The towards this point on the anterolingual root in convex lingual surface of the root is continuous occlusal view (particularly on QM F23774) and dif- with the convex lingual surface of the crown. The fers in this respect from M2-4. The lingual margin apex of the anterolingual root points slightly poste- on the posterior half of the posterior moiety is rela- riorly (and buccally). The buccal constriction is con- tively flat and faces posterolingually in occlusal tinuous with the division between anterobuccal and view. The buccal constriction is relatively flat and posterior roots. The lingual constriction is approxi- wide (anteroposteriorly) in occlusal view. Immedi- mately continuous with the division between anter- ately posterior to the buccal constriction the buccal olingual and posterior roots. There is a single surface is slightly flat or concave. apical foramen on the medial surface of each root. There is a significant decrease in enamel M1. There is limited evidence regarding cusps on height on the lingual surface of M1 with enamel M1. What can be inferred is based mainly on inflec- decreasing from a maximum on the anterior moiety tions of the buccal and anterior margins in occlusal to a minimum anterior to the midpoint on the poste- view. This is best seen on QM F30339 (Figure 5.1). rior moiety. The EDJ is almost vertical across the There is a distinct convexity located on the buccal constriction on QM F30339. The enamel height margin in the stylar cusp C (StC) position on QM minimum is approximately coincident with, or F30339. Anterior to this convexity the enamel mar- slightly posterior to, the division between anterolin- gin faces anterolingually and is relatively flat. gual and posterior roots. Posterior to this minimum, Immediately below this, the occlusal surface is enamel height increases slightly before decreasing slightly concave. A deep groove in the margin is again onto the posterior surface. present anterior to this (in profile view and extend- The lingual constriction at the occlusal surface ing posterobasally down the buccal enamel surface is located anterior to the enamel minimum and the for a short distance as a concavity in the enamel). division between the anterolingual and posterior Immediately anterior to the groove the margin is roots. It is relatively deep close to the occlusal sur- inflected buccally again at a convexity that is simi- face but fainter, basal to the occlusal surface. The lar in overall size to that adjacent to the constric- constriction forms an angle of approximately 85° to tion. The anterior convexity is located in the stylar the occlusal surface and curves posteriorly and cusp B (StB) position. The buccal surface is basally away from the occlusal surface as a semi- broadly convex for some distance basal (and pos- continuous and slightly sinuous groove. terobasally) to this. Enamel height on the posterior surface is rela- Although the anterobuccal corner is damaged tively small, increasing in height only slightly mid- on all M1 specimens, there appears to be a para- way between enamel minima on posterobuccal stylar region located anterior and slightly lingual to and posterolingual ‘corners’. The extensive enamel StB. An enamel remnant is present on the occlusal cover on the anterior half of the lingual surface surface of QM F23774 immediately posterolingual extends onto the anterior surface. Enamel height to the parastylar region. This remnant probably decreases significantly over the anterolingual root represents the anterior basin based on compari- on the anterior surface. The basal EDJ is approxi- sons with the posterior molars on this specimen. mately 80° to the occlusal surface at this position. An enamel remnant is also present adjacent to the Enamel height is smallest just lingual to the division buccal constriction on the occlusal surface of all between anterobuccal and anterolingual roots. The M1s. This latter remnant probably represents the basal EDJ is approximately horizontal between this buccal end of the transverse valley. On QM point and the anterobuccal ‘corner’. Enamel is thin- F23725 and QM F30339 there is a minor groove nest on the anterior and posterior surfaces and at on this latter enamel remnant that is located poste-

11 BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH

the constriction on the buccal surface where view, the lingual constriction is continuous and bet- enamel height is smallest. ter defined than on M1. It curves posteriorly and The secondary occlusal wear surface is deep- basally. A distinct parastyle is not obvious on M2 est along an anteroposterior band that is closer to based on the occlusal outline. Distinct inflections in the lingual margin than the buccal margin on QM the StB and StC positions are not obvious on M2. F23725. On QM F30339, wear is greatest near the The buccal margin may be slightly inflected lin- centre of the occlusal surface and at the anterior gually midway between the anterior edge of the and posterior margins midway between buccal and tooth and the constriction, but this is not certainly lingual surfaces. The occlusal dentine on QM the case. There may also be a slight lingual inflec- F30339 undulates slightly. There are two faint tion midway along the buccal margin on the poste- ridges in the occlusal dentine that are orientated in rior moiety, but again this is not certain because an anterolingual-posterobuccal direction on QM both M2 specimens are slightly damaged. F30339. The posterior ridge is restricted to the pos- The anterior and posterior basins are better terior moiety (Figure 5.1); the anterior ridge is preserved on M2 relative to M1, and they appear to fainter than the posterior ridge and extends be confluent with the crests which form the anterior between the notch on the anterior half of the buccal and posterior margins of the tooth, respectively. surface (near to where the paracone is on the pos- The anterior and posterior crests are very narrow terior molars) and the anterolingual corner of the (anteroposteriorly). The anterior crest slopes tooth. The occlusal dentine is broadly concave anterobasally and the posterior cingulum slopes anterior and posterior to these ‘pseudolophs’. Pul- posterobasally. There may be a very minor crest pal cornua are exposed at the occlusal surface on between the respective basins and crests but it is the anterior and posterior moieties of QM F30339. not clear on either specimen. The posterior basin 1 All M root measurements were taken on QM appears to be slightly lower (i.e., more basal) than F30339. Root dimensions were measured at the the anterior basin. The anterior moiety projects interradicular furcation. Anterobuccal and poste- higher above the alveolus than the posterior moi- rior roots are approximately 3 mm in anteroposte- ety, particularly on the buccal side. The roots below rior width, and the anterolingual root is 3.5 mm in the level of the alveolus are not visible. anteroposterior width. Buccolingual root width is M3. M3 is similar to M2 except as follows. There are 2.5 mm on the anterobuccal root, 4.5 mm on the no obvious stylar cusps; however, the buccal mar- posterior root and 3 mm on the anterolingual root. gin is worn on the posterior moiety of both speci- The posterior root has two tightly curved corners mens. In addition, there are faint grooves and (buccal and lingual edges) and two broadly curved bumps all over the occlusal surface and on the surfaces (anterior and posterior surfaces). In pos- occlusal margins. Most of these are only just visible terior view the buccal edge of the posterior root is to the naked eye. The lingual constriction is even almost vertical, and the lingual edge slopes buc- 2 cally towards the root apex. In contrast, the antero- narrower than on M and remains very narrow lingual root does not taper significantly until 3 mm away from the occlusal surface. The posterior half below the furcation at the position of the apical of the lingual margin on the posterior moiety is not 2 foramen. All three roots have single and simple as flat as it is on M . There is a very distinct lin- apical foramen and a groove on the medial surface gually- and basally-sloping wear facet on the lin- of the root adjacent to the interradicular furcation. gual enamel at the constriction on QM F23725. The furcation between the anterolingual root and The facet is widest (buccolingually) at or just ante- posterior root is slightly lower (further away from rior to the constriction and tapers anteriorly and the occlusal surface) than that between the antero- posteriorly. The posterior basin is lower on the buccal and posterior roots. The anterobuccal root occlusal surface (more basal) than the anterior has a fairly well developed ridge on its anterior sur- basin. face. Greater detail is visible on the occlusal sur- 3 2 M2. Similar to M1 except for the differences out- face of M (particularly on QM F23774) than on M . Grooves extend anterolingually and posterolin- lined below. The overall shape of M2 is more rect- gually from a point just lingual to where the anterior angular and bilobed than that of M1. The posterior loph meets the buccal margin. The low point on the half of the posterior moiety on the lingual side is anterior and posterior lophs is approximately mid- distinctly flat and faces posterolingually. The lingual way between buccal and lingual margins. The 1 constriction is narrower than on M ; however, this anterolingual groove extends into the anterior 1 may be related to greater wear on M . In lingual basin. The posterolingual groove extends as far as

12 PALAEO-ELECTRONICA.ORG

the transverse valley. Grooves extend anteriorly anterior loph at its lowest point (which is closer to and posteriorly from the low point on both lophs. the lingual margin than the buccal margin). The There may be a slight offset between these groves posterior continuation of this groove is approxi- at the transverse valley on QM F23774 with the mately anteroposterior in orientation until it meets groove extending posteriorly from the anterior loph the transverse valley. The anterobuccal groove of meeting the transverse valley buccal to the groove the anterior basin meets the buccal half of the extending anteriorly from the posterior loph. In anterior loph lingual to the buccal margin. It between these points within the transverse valley appears to continue posterior to the loph as far as is the termination of a low ridge that extends pos- the transverse basin but is very faint. terobuccally from the approximate position of the The lingual surface posterior to the apex of protocone (not preserved on either specimen). The the protocone is fairly convex and the enamel is transverse valley is sinuous around this projection, relatively thick. In contrast, the lingual surface and the buccal half of the valley is anterolingual- either side of the constriction is relatively thin and posterobuccal in orientation. In contrast, the trans- flat. Immediately anterior to the constriction, the lin- verse valley on QM F23725 is relatively straight gual surface slopes lingually at a shallow angle for and buccolingual in orientation. a short distance below the occlusal surface, There is a relatively high crest that forms the whereas it dips more steeply posterior to the con- buccal half of the anterior margin on QM F23774 striction. Away from the occlusal surface the lingual (the occlusal surface of QM F23725 is more worn surface either side of the constriction is more con- than that of QM F23774). The crest appears to vex. In lingual view, the lingual margin slopes decrease in height lingually towards the point basally towards the constriction to from a wide ‘v’. where a groove that extends anteriorly from the The posterior loph is coincident with the pos- anterior basin meets the anterior margin. In con- terior margin of the occlusal surface on M4. It is rel- trast to the anterior basin, the posterior basin is not atively straight and buccolingual in orientation. bounded posteriorly by a crest. The buccal surface Immediately below the occlusal surface, the poste- curves lingually immediately posterior to the proba- rior surface slopes posterobasally at a slightly dif- ble location of the metacone on unworn specimens ferent angle to the rest of the posterior surface. and is continuous with the posterior surface of the Below this, the posterior edge of the tooth is posterior loph. The posterior surface of the loph strongly convex in occlusal view. The posterior drops steeply posterobasally towards the posterior margin of the occlusal surface is highest at the margin of the tooth. Faint grooves on the posterior metaconule. surface of the loph extend posterobasally towards The metaconule is located on the posterolin- the posterior margin. gual corner and is relatively low and almost indis- M4. The posterior moiety on M4 is around two- tinguishable from the posterior and lingual margins. thirds the width and length of the anterior moiety. It It is roughly pyramidal. The posterior and lingual is also lower in occlusal height than the anterior surfaces of the metaconule are steep and rounded. moiety. The buccal and lingual constrictions are The anterobuccal face is almost triangular and is relatively shallow. The protocone is located on the broad, flat and shallowly dipping. The metacone anterolingual ‘corner’ of the occlusal surface; how- apex was probably located just anterior to the pos- ever, the paracone is located midway between the terobuccal corner; however, the occlusal surface is anterobuccal ‘corner’ and the constriction. The worn at this position. The metacone was probably anterior loph is therefore orientated in a slightly quite low and not particularly cuspate. The tips of anterolingual-posterobuccal direction. The anterior all of the cusps are worn flat. basin is wider (anteroposteriorly and buccolin- The transverse valley appears more bowl-like gually) and shallower than on M1-3. Grooves relative to the anterior molars and may be slightly extend anterobuccally, anterolingually, posterobuc- shallower. The buccal half of the transverse valley cally and posterolingually from the anterior basin. bounds the anterior face of the metacone. The The anterobuccal and anterolingual grooves deepest point in the transverse valley is located extend as far as the anterior margin and bracket just buccal to the lingual margin where the poste- the anterior-most point on the tooth. Although rior continuation of the groove from the low point poorly defined, this anterior ‘projection’ may be on the anterior loph meets it. A groove extends equivalent to the parastyle on M1. It is located buc- posterobuccally from this low in the transverse val- cal to the midpoint between buccal and lingual ley. It intersects the posterior margin just lingual to margins. The posterolingual groove meets the the posterobuccal corner adjacent to the

13 BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH

metacone. This groove is probably equivalent to posteriorly) at the occlusal surface and shortest the groove that extends between the transverse midway between the occlusal surface and the fur- valley and the low point on the posterior loph on cation between the roots. The tooth is widest (buc- M3. The buccal half of the posterior moiety is thus colingually) at or just below the level of the reduced in size relative to the lingual half on M4. furcation (due to the curvature of the buccal sur- Enamel extends as far as the alveolar margin face). on the lingual and posterior surfaces of M4 on QM The constriction between the moieties is F23774. The enamel on the anterior surface is broad and relatively flat on the lingual side and nar- largely obscured by M3. Enamel height decreases rower and more ‘pinched-in’ on the buccal side in on the anterior surface to a minimum just posterior occlusal view. It is represented by a groove in the to the anterobuccal corner of the tooth. Enamel enamel that extends to the base of the enamel on height on the buccal surface increases posterior to the buccal surface and is approximately continuous this to a maximum located below (basal) and just with the furcation between the roots. On the lingual posterior to the anterior loph. Enamel height surface, the small enamel height and the poor con- increases slightly again posterior to this to a mini- dition of the lingual enamel on this specimen mum just anterior to the buccal constriction. There means that a distinct groove, if it was present, can- is a slight increase in enamel height below the con- not be discerned below the occlusal surface. striction. Enamel height increases posterior to the Enamel surrounds the dentine of the occlusal constriction and onto the posterior surface. wear surface of the tooth, although enamel height Lower Dentition. The molars are bilobed. Anterior is variable. Enamel height is greatest on the buccal and posterior moieties are fairly rounded in occlu- surface, where enamel extends as two narrow sal outline. Occlusal cusp morphology is not pre- tracts down anterior and posterior roots. Enamel served on either lower molar specimen due to extends a significant distance below the furcation wear. The secondary occlusal wear surface con- between the roots on this surface, particularly on sists of an enamel perimeter surrounding dentine. the anterior root. Both enamel tracts taper towards Enamel height is greatest, and is extensive, on the the root apices. Enamel height decreases signifi- buccal surface but is fairly small (occlusobasally cantly between the roots from a height of at least 6 restricted) on all other surfaces. Enamel is also mm on the roots (the full extent being obscured by thickest on the buccal side. cementum) to 2.1 mm at the buccal constriction. There are two roots: an anterior root (located Enamel height decreases onto anterior and poste- beneath the anterior moiety) and a posterior root rior surfaces. Enamel is thickest on the buccal sur- (beneath the posterior moiety). The roots lean face and is approximately 0.4 mm thick. towards the posterior surface on QM F51404 (i.e., Enamel cover on the lingual surface is much the root apices are closer to the posterior surface less extensive than that on the buccal surface. of the teeth than the anterior). The orientation of Enamel height increases only slightly over anterior QM F23773 is unknown, but the posterior surface and posterior roots on the lingual surface. The is tentatively identified as the one to which the base of the enamel remains a significant distance roots lean on this latter specimen. Thin cementum above the furcation between the roots on this side. covers the surfaces of the roots and extends over Enamel height decreases slightly at the lingual the enamel. constriction and onto the posterior surface. There M . Anterior and posterior moieties are similar in is little change in enamel height towards the anter- 1 olingual ‘corner’ of the tooth except due to varia- anteroposterior length, although the posterior moi- tions in height of the occlusal surface as a result of ety is slightly longer than the anterior moiety, par- wear. ticularly on the buccal side (Figure 5.2). The On the anterior surface, enamel height anterior moiety is smaller in buccolingual width rel- decreases from a maximum at the anterobuccal ative to the posterior moiety (4.0 mm and 5.0 mm, ‘corner’ to a minimum midway across the surface. respectively). The anterior moiety narrows towards The base of the enamel between these two points the anterior of the tooth and is particularly narrow forms an angle of approximately 60° to the occlusal towards the occlusal surface. In contrast, the pos- surface. Lingual to the midpoint on the anterior sur- terior moiety is much wider and rounder. The pos- face, there is a very slight increase in enamel terior surface is broad and flat. The buccal surface height before enamel height decreases again and is broadly convex and the lingual surface is rela- continues to do so (at a very shallow angle) as far tively flat. The root surfaces are continuous with as the anterolingual ‘corner’. There is a slight the crown surfaces. The crown is longest (antero-

14 PALAEO-ELECTRONICA.ORG

groove in the enamel on the anterior surface, just thinner and more irregular in profile than the buccal lingual to the anterobuccal ‘corner’. enamel as a result of extensive chipping of the for- On the posterior surface, enamel height mer. The lingual enamel is rounded where chipping decreases at an angle of approximately 45° to the has taken place. The posterior half of the lingual occlusal surface from the posterobuccal ‘corner’ to enamel on the posterior moiety is particularly a minimum that is lingual to the midpoint on the chipped, and there is a relatively large triangular surface. Lingual to this, enamel height increases wedge of enamel missing midway across the lin- slightly towards the posterolingual ‘corner’ at an gual enamel on the anterior moiety. The occlusal angle of about 40°. The base of the enamel either dentine is continuous with the inner (buccal) edge side of the minimum on this surface is broadly con- of the lingual enamel. cave. The enamel height minimum is located just The anterior half of the anterior moiety is dom- lingual to a topographic low (due to wear) on the inated by a distinctive wear facet that slopes anteri- posterior margin of the occlusal surface. The orly, basally and slightly buccally. The facet enamel on the posterior surface is flat as a result of extends across the enamel-dentine junction with tooth wear. the enamel and dentine being flush with one Original cusp detail is not preserved and has another. The facet itself appears slightly curved been replaced by a secondary wear surface char- (anteroposteriorly) and has well-defined edges. acterised by an enamel perimeter and central den- The wear facet is bounded posteriorly by a ridge of tine. The dentine is concavely worn with the central dentine that forms a buccolingual topographic high. valley being anteroposterior in orientation. The This ridge is rounded and is approximately parallel deepest point on the occlusal surface is midway to the pseudoloph in the dentine of the posterior between buccal and lingual surfaces and slightly moiety. The occlusal surface immediately posterior posterior to the constriction between the moieties. to this ridge is concave and curves steeply basally The dentine of the occlusal surface slopes towards towards the centre of the wear surface. There is a the central valley at a slightly shallower angle on change in orientation and angle of this slope mid- the buccal side relative to the lingual side. There is way down. only a slight increase in the height of the occlusal The dentine ridge that forms the posterior dentine towards the posterior edge of the tooth, boundary of the anterior facet meets another crest and the low point on the posterior perimeter is con- of dentine at its lingual edge. The latter crest tinuous with the central wear valley. extends posterolingually from this junction and The central dentine is continuous with the forms the lingual boundary of the occlusal surface ‘push’ side (inner or lingual edge; Koenigswald et where the enamel edge has been extensively al., 1994) of the enamel perimeter on the buccal chipped. The anterior confluence of these two den- side so that they form a continuous facet (although tine crests is the highest point on the occlusal wear in places a small step between the two is devel- surface. If this point also formed a topographic high oped). This facet between the enamel and dentine when the anterior lingual edge was bounded by is buccolingually narrower either side of the buccal enamel rather than dentine, there may well have constriction, but increases in width towards the been a concentration of occlusal pressure at this posterobuccal ‘corner’ of the tooth. The ‘pull’ side position. In addition, the high angle of the anterior (outer or buccal edge; Koenigswald et al., 1994) of wear facet compared to the rest of the wear sur- the buccal enamel on the posterior moiety is face indicates that multi-directional stresses would rounded (convex). There may be a thin facet adja- have been acting on the lingual enamel. It is there- cent to the constriction on this edge, but it is not fore no surprise that failure of the lingual enamel clear. In buccal view, the occlusal profile is rela- occurred, such as that resulting in the large trian- tively flat and broadly concave across the buccal gular gap in the enamel. constriction and the midpoints on anterior and pos- The furcation between the roots is slightly terior moieties form topographic ‘highs’. A low higher (more occlusal) on the lingual side relative pseudoloph in the dentine of the occlusal surface to the buccal side. As a result, the furcation slopes extends lingually and slightly anteriorly from the away from the occlusal surface towards the lingual posterior topographic high as far as the central side. Both roots are wider buccolingually than wear valley. anteroposteriorly and taper towards the lingual The outer surface of the buccal enamel is side. The medial surface of the roots is shallowly irregular. This is probably a reflection of a complex concave. The apical foramen is preserved on the enamel-cementum interface. The lingual enamel is posterior root, 1.9 mm occlusal to the root apex.

15 BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH

The medial surface is deeply grooved between the decreases at the lingual constriction and onto ante- apical foramen and the root apex. rior and posterior surfaces. M2/M3. QM F23773 is an M2 or M3 (Figure 5.3). It On the anterior surface of the tooth, the basal is similar to M1, differing mainly in the greater simi- EDJ is highest (closest to the occlusal surface) just larity between anterior and posterior moieties and buccal to the anterolingual ‘corner’. Enamel height absence of the anterior wear facet and taper. The increases only slightly between this point and a posterior moiety is slightly smaller in anteroposte- point just lingual to the anterobuccal ‘corner’ of the rior length than the anterior moiety, but is greater in tooth. Buccal to this, there is a significant increase buccolingual width. The tooth is longest at the in enamel height onto the buccal surface with the occlusal surface and shortest (anteroposteriorly) at EDJ approaching vertical. There is also a slight the level of the interradicular furcation. The con- increase in enamel height at the anterolingual ‘cor- striction is well developed in occlusal view on buc- ner’. Minimum enamel height is centrally located cal and lingual sides. on the anterior surface due to a topographic low on The anterior surface of the tooth is flat and the enamel perimeter at this position (i.e., in pro- slopes basally away from the occlusal surface. file). Posterior to the anterobuccal ‘corner’ of the tooth On the posterior surface, the basal EDJ is (on the buccal surface) is a groove that extends highest at the posterolingual ‘corner’. Enamel basally and slightly posteriorly away from the height increases between this point and the pos- occlusal surface. The occlusal outline appears terobuccal ‘corner’, where the enamel is extensive. slightly ‘pinched in’ (buccolingually) between this The basal EDJ slopes at an angle of approximately groove and a similar position on the lingual margin. 30° to the occlusal surface, although it increases in Immediately anterior to this, the anterobuccal and angle slightly towards the posterobuccal ‘corner’. anterolingual ‘corners’ are relatively convex (in Minimum enamel height is located just lingual to comparison with the posterobuccal and posterolin- the midpoint on the posterior surface due to a topo- gual corners) and emphasise the flat anterior edge. graphic low on the enamel perimeter at this posi- The anterior moiety is relatively symmetrical about tion. the median anteroposterior plane of the tooth and The central dentine of the occlusal surface is differs from the posterior moiety in this respect. concave, being deepest along an anteroposterior The posterior moiety is longer (anteroposteriorly) axis located just lingual to the midpoint between on the lingual side relative to the buccal side. The buccal and lingual surfaces. This axis of greatest posterior-most point on the tooth is buccal to the wear intersects the anterior and posterior edges of midpoint on the posterior surface. Lingual to this, the occlusal surface at topographic lows. In ante- the posterior surface is relatively flat and faces rior and posterior view, the occlusal surface ‘v’s to slightly posterolingually. In contrast, the buccal half these low points. Occlusal wear on the anterior and of the posterior surface is more broadly convex. posterior moieties resembles that on the posterior Enamel surrounds the occlusal surface and is moiety of M1. There is a small step between the thicker than on M1, although this may be partially central dentine and the buccal enamel (the dentine or wholly a result of differing amounts of occlusal being worn lower) although dentine and enamel wear between these tooth positions. Enamel is are nearly flush with one another. The buccal thickest (up to 0.5 mm) on the buccal side and at enamel is rounded on both ‘push’ and ‘pull’ sides the anterobuccal ‘corner’. Enamel is extensive on with no clear well-defined facets. In buccal view, the buccal surface, particularly over the roots. The the buccal enamel is relatively flat at the occlusal enamel extends below the interradicular bifurcation surface although it is worn slightly lower at the con- onto the roots on the buccal side. There is a striction relative to the buccal margin anterior and decrease in enamel height from the buccal surface posterior to it. In a similar manner to M1, the lingual onto anterior and posterior surfaces, with the great- enamel shows evidence of chipping with some of est decrease being onto the anterior surface. the fractured edges of the enamel being rounded. Enamel height also decreases at the buccal con- There are vertical cracks in the lingual enamel. The striction (above the interradicular bifurcation). central dentine and lingual enamel are flush with Enamel height on the lingual surface is much less one another. extensive. There is a slight increase in enamel Crown height on the buccal side (i.e., the dis- height over the roots on the lingual surface. This is tance between the interradicular bifurcation and emphasised by the greater topographic height of the occlusal surface) is 5.6 mm. Both roots are 8.4 the occlusal enamel at this position. Enamel height mm in dorsoventral length between the interradicu-

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lar furcation and the root apices. The anterior root much better developed in R. crowcrofti forming a is 2.9 mm in anteroposterior width (on the buccal pattern of enamel and dentine tracts around the side) and 5.1 mm in buccolingual depth, measured tooth that broadly correspond to those of hypsel- just below the bifurcation. The posterior root is 3.2 odont wombats (particularly species of Warendja). mm in anteroposterior width and 5.5 mm in bucco- Similarities between R. crowcrofti and N. boodjam- lingual depth. The apical foramen is located 3.7 ullensis include the presence of a wider anterior mm above the root apex on the medial surface of moiety below the occlusal surface on M1 (partly the anterior root and 4.3 mm above the apex on due to a projecting anterolingual root), the the medial surface of the posterior root. The medial decrease in lingual enamel height between the surface is grooved between the apical foramen and anterior and posterior moiety on M1 and the con- the apex on both roots. striction between the anterior and posterior moi- Comparisons eties sloping posteriorly away from the occlusal surface in lingual view on the upper molars. In Nimbavombatus boodjamullensis is a small, addition, N. boodjamullensis and R. crowcrofti are plesiomorphic vombatid. It is similar in size to the the only vombatids with rooted cheek teeth. Pleistocene Warendja wakefieldi, previously the The unworn occlusal morphology of the cheek smallest vombatid known (Appendix 3). Using the teeth is not known for any extinct vombatid with the regression equations in Myers (2001) both N. boo- exception of Warendja encorensis (Brewer et al., djamullensis and W. wakefieldi are estimated to 2007). This is because cusp details are only pre- have had a body mass between 6,000 and 9,000 g served in very young individuals in wombats, and (using upper molar row length as a proxy, as well that wombats are relatively rare components of as M2 length in combination with upper molar row most faunas. In W. encorensis, interpretation of the length). This is similar to slightly larger than a mod- cusps on the two juvenile molar specimens avail- ern koala. In contrast, R. crowcrofti is estimated to able is confounded by uncertainty regarding tooth have had a body mass of between 50,000 and position. Comparisons of cusp details with N. bood- 60,000 g (using lower molar length): an order of jamullensis are thus largely limited to the modern magnitude larger than that of N. boodjamullensis. taxa, V. ursinus and L. latifrons (Appendix 4). The N. boodjamullensis specimens are unlikely to Nimbavombatus boodjamullensis molars are be juveniles because the roots are fully closed, the bunodont with stylar cusps reduced or absent, and occlusal surfaces have undergone relatively large paracone and metacone located on the buccal amounts of occlusal wear, and there are two simi- margin. This contrasts with the upper molars of V. larly sized individuals from two different deposits at ursinus and L. latifrons as well as other non-lopho- Riversleigh. dont vombatiform marsupials where stylar cusps The combination of broad inflections in are expressed quite strongly on the upper molars. enamel height around the cheek teeth, thickened It is possible that the simplified, bunodont occlusal enamel on the lingual surface of the upper molars morphology on N. boodjamullensis is apomorphic and buccal surface of the lower molars, simple P3 for this taxon. with small parastyle, crest-like parametacone and In addition to the characters listed above, the small posterolingual crest and valley identify N. upper molars of N. boodjamullensis also differ from boodjamullensis as a vombatid. The combination those of V. ursinus in the absence of a well-devel- of rooted cheek teeth, with cusp detail preserved in oped parastyle on M2-4, in the lack of expansion of the adult dentition, presence of a C1 and I2 and/or the anterior parastylar region and the absence of I3, minor inflections in enamel height around the crenulations in the enamel (in the form of minor cheek teeth (compared to other vombatids) identify cusps and crests) that can be seen on the unworn N. boodjamullensis as the most plesiomorphic occlusal surface of V. ursinus molars (Appendix 4). vombatid known. Estimated to be early Miocene in They differ from those of L. latifrons in that the age, it is also one of the oldest vombatids known. parastyle is better developed on M1 and in the The only other vombatid described from deposits anterior location of the metacone relative to L. lati- older than late Miocene is Rhizophascolonus crow- frons. The molars of N. boodjamullensis differ from crofti, which is known from isolated teeth from early those of V. ursinus and L. latifrons in the rectangu- to middle Miocene deposits of South Australia and lar-shaped occlusal outline (in occlusal view). Queensland (Archer et al., 1997). The molars of R. Upper molars of N. boodjamullensis differ crowcrofti are similar to those of N. boodjamullen- from those of W. encorensis in the absence of a sis; however, the inflections in enamel height are high anterior margin, presence of relatively low

17 BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH

FIGURE 6. Lingual view of lower molars to show presence of enamel tracts (indicated by asterisks). 1, Nimbavomba- tus boodjamullensis. 2, Rhizophascolonus crowcrofti. 3, Warendja encorensis.

bunodont cusps, presence of a simple, non-bifur- on M1 in both N. boodjamullensis and R. crowcrofti. cated medial crest connecting the main cusps in We have not observed a dentine tract at this posi- each moiety and the greater similarity in height tion in other vombatids. The difference in enamel between anterior and posterior moieties. height between anterior and posterior moieties on The overall pattern of inflections in enamel the lingual surface is not as pronounced towards height around the cheek teeth is similar in N. bood- the posterior end of the molar row in N. boodjamul- jamullensis and R. crowcrofti. Enamel height min- lensis and R. crowcrofti. ima tend to be relatively broad on N. The molars of N. boodjamullensis, R. crow- boodjamullensis in comparison to R. crowcrofti and crofti and species of Warendja differ from all other the inflections in the enamel height tend to be less vombatids in the shape of the occlusal outline (in sharp. Enamel minima and maxima in N. boodjam- occlusal view), being only slightly inflected at the ullensis and R. crowcrofti broadly correspond to lingual constriction on the upper molars and at the the pattern of dentine tracts and enamel tracts in buccal constriction on the lower molars. The species of Warendja (Figure 6). The relative widths extreme inflections on the lingual side of the of the dentine tracts in the latter are more similar to uppers and buccal side of the lowers of all other R. crowcrofti than N. boodjamullensis. vombatids are not seen in any other Australian Enamel extends below the level of the interra- marsupial. The relatively shallow depth of these dicular furcation and onto the surface of the roots inflections in N. boodjamullensis, R. crowcrofti and on the lingual side of the upper molars, buccal side species of Warendja is therefore symplesiomor- of the lower molars and on the anterior root of P3 in phic. N. boodjamullensis and R. crowcrofti. Enamel Rhizophascolonus crowcrofti and N. boodjam- height on the lingual surface is markedly smaller on ullensis are the only vombatids for which the ante- the posterior moiety relative to the anterior moiety rior moiety on M1 is wider than the posterior

18 PALAEO-ELECTRONICA.ORG

moiety. The similarity between M1 in N. boodjamul- and Pledge, 1987; Brewer, 2007). The ventral root lensis and R. crowcrofti is probably partly due to slopes laterally as a shelf in N. boodjamullensis, the projecting lingual root. The difference in width whereas in W. wakefieldi it forms a relatively shal- between the moieties is least at the occlusal sur- low convexity for about 7 mm before flaring later- face and increases away from it (as a result of the ally at the maxillojugal suture. There is a dish- projecting lingual root). However, the relative width shaped infraorbital fossa in W. wakefieldi. In con- of the moieties is variable between specimens and trast, in N. boodjamullensis this area is relatively is dependent on where the measurement is taken flat and slightly convex. The height between the for both taxa. The narrow occlusal surface of the alveolar margin and the dorsal surface of the zygo- anterior moiety of M1 in pouch young specimens of matic arch is much greater in W. wakefieldi than N. V. ursinus and L. latifrons is very distinctive (partic- boodjamullensis. The posterobasal slope of the ularly in L. latifrons) and is not shared by N. bood- dorsal surface of the alveolar process (maxillary jamullensis. shelf) is also greater in W. wakefieldi as a result of In contrast to the narrow anterior moiety on the presence of hypselodont teeth in the latter that M2 of V. ursinus and L. latifrons, the anterior moiety decrease in occlusobasal length from M1 to M4. on M2 or M3 is usually the widest part of the molar The anterior margin of the maxillary vacuity is 2 row in N. boodjamullensis. M4 in N. boodjamullen- located medial to the posterior moiety of M in both sis and R. crowcrofti is generally narrower than M4 N. boodjamullensis and W. wakefieldi. The width of in V. ursinus and L. latifrons. It is similar in relative the palate between the median palatine suture and 1 2 width to Phascolonus gigas. All vombatids have a the alveolar margin at M and M is similar in W. narrower posterior moiety than anterior moiety on wakefieldi and N. boodjamullensis (relative to over- M4. all size). The P3 of N. boodamullensis is similar to that RESULTS OF THE PHYLOGENETIC ANALYSIS of V. ursinus and L. latifrons in that it is dominated by the parametacone crest with a poorly developed Three minimally parsimonious trees were parastylar region and a low-lying posterolingual generated when all taxa were included in the anal- crest. It differs from them in that the paracone dom- ysis. All trees had 229 steps, a Consistency Index inates the occlusal surface, and the metacone is (CI) of 0.6445, a Retention Index (RI) of 0.7070 much more crest-like than the paracone. There is and Rescaled Consistency Index (RC) of 0.4755. an inflection of the anterolingual surface just poste- The only thing that changed regarding the topolo- rior to the parastyle on P3 in N. boodjamullensis gies of these trees was the position of Marada that is in a similar position to the distinctive antero- arcanum (strict consensus tree shown in Figure lingual groove on the adult P3s of V. ursinus and L. 7.1). Hence, this taxon was excluded and the anal- latifrons. ysis was re-run. The result was a single most parsi- monious tree with the same topology as the The M1 of N. boodjamullensis resembles that of all other wombats (with the exception of some previous trees, but without M. arcanum (Figure specimens of P. gi g as and Ramsayia lemleyi) in 7.2). This tree has 228 steps and CI = 0.6476, RI = that the anterior moiety is narrower than the poste- 0.7028 and RC = 0.4747. Unambiguous apomor- rior moiety. The anterior moiety on M forms a phies are given in Appendix 5. 1 Bootstrap support was high (98%) for a mono- topographic high just posterior to the anterior edge phyletic ingroup and for Diprotodontoidea (i.e., of the tooth in N. boodjamullensis. This wear profile Diprotodontidae + Palorchestidae). Support was is also seen in early wear stages in V. ursinus and moderate (78%) for a monophyletic Vombatidae L. latifrons M s and is located at the position of the 1 with three unambiguous apomorphies supporting protolophid. In Warendja, the anterior topographic this group: pattern of enamel/dentine tracts on high on M1 is coincident with the anterior surface of molars and premolars and the absence of a mas- the tooth rather than just posterior to it. It is possi- seteric process. Support was poor (< 60%) for the ble that this is related to a much reduced or absent arrangement of the other taxa. Within Vombatidae anterior cingular region and paracristid in Warendja there is moderate support (76%) for monophyly of relative to the other taxa. hypselodont wombats based on three unambigu- The anterior ventral root of the zygomatic arch ous apomorphies: loss of C1, presence of hypsel- is located above the anterior moiety of M2 in N. odont cheek teeth and the extension of enamel boodjamullensis. In W. wakefieldi it is located tracts down outer surfaces of the cheek teeth. Nim- above the contact between M2 and M3 (Flannery bavombatus boodjamullensis and R. crowcrofti

19 BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH

FIGURE 7. 1, Strict consensus tree for parsimony analysis including Marada arcanum. 2, Bootstrap support for sin- gle most parsimonious tree from analysis excluding Marada arcanum (see text for details). Vombatidae indicated in purple. form a sister group to the hypselodont wombats, hypselodont wombats, these taxa do shed light on but are united based on a single unambiguous possible intermediate stages in the evolution of the apomorphy: enamel height on posterior moiety of tooth morphology (and related cranial and mandib- M1 smaller than on anterior moiety in lingual view. ular adaptations) of modern wombats. Evolution of Enamel and Dentine Tracts DISCUSSION The evolution of dentine tracts based on Regardless of whether N. boodjamullensis inflections in enamel height was documented in and R. crowcrofti are directly ancestral to the geomyoid rodents (Rensberger, 1971, 1975), and a

20 PALAEO-ELECTRONICA.ORG

similar mechanism appears to be responsible for striction between the moieties on the leading edge the evolution of dentine tracts in wombats. Under and on anterior and posterior surfaces. Moving this model, small inflections in enamel height from N. boodjamullensis to R. crowcrofti and spe- around the perimeter of the tooth become exagger- cies of Warendja, differences in enamel height and ated over time. In taxa that have hypselodont teeth, thickness as well as in width of the tracts become these inflections can be observed on the occlusal more pronounced over time. Leading edge enamel enamel cap of very young individuals. This enamel is eventually lost and enamel becomes continuous cap is worn away early in ontogeny and enamel across the trailing surface. Traces of this evolution- height minima are then represented by dentine ary history can be traced in the inflections in tracts. Using the terminology of Tummers and enamel height on the enamel caps of juvenile Thesleff (2003), a switch to a 'root fate' occurs molars of V. ursinus and L. latifrons. early in tooth development at those positions rep- Mastication in Wombats resented by dentine tracts (i.e., enamel production ceases), whilst this switch does not occur where Jaw movement during the power stroke in enamel tracts are present. mastication is wholly transverse in V. ursinus and The inflections in enamel height and thickness L. latifrons (Ferreira et al., 1989; Murray, 1998; around the molars of N. boodjamullensis and R. Crompton et al., 2008b), and this was probably crowcrofti broadly correspond to the pattern of also the case in Ramsayia, Phascolonus and enamel and dentine tracts present around the “Phascolomys” due to the similarity in molar mor- molars in both species of Warendja, with the inflec- phology between these taxa and extant wombats. tions in enamel height being more pronounced in The lower molars on the working side of the jaw species of Warendja than R. crowcrofti, which in move medially and slightly anteriorly across the turn are more pronounced than in N. boodjamullen- upper molars in a single movement. Enamel is sis (Figure 6). Species of Warendja, R. crowcrofti restricted to the trailing edge of the molars (lingual and N. boodjamullensis all possess two enamel surface of the upper molars and buccal surface of tracts on the leading edges of the molars (buccal the lower molars) as well as those parts of the surface of the upper molars and lingual surface of anterior and posterior surfaces which form part of the lower molars). They differ in this respect from the enamel cutting edge. all other wombats, where enamel is absent on the Enamel is thickest and most extensive on the leading edge of adult molars (except as aberra- trailing edge of the molars in N. boodjamullensis. tions), although enamel tracts can sometimes be This is confirmed by the presence of a step seen in juvenile specimens of V. ursinus and L. lat- between the central dentine and trailing edge ifrons (e.g., NMV C10928). If we imagine an evolu- (Greaves, 1973; Rensberger, 1973; Costa and tionary sequence starting with N. boodjamullensis, Greaves, 1981). In contrast, the enamel on the passing through R. crowcrofti and then Warendja leading edge (buccal surface of the upper molars and finishing with V. ursinus/L. latifrons we have a and lingual surface of the lower molars) is always plausible model for the evolution of the modern flush with the central dentine. Pseudolophs in the pattern of enamel around the perimeter of wombat central dentine on QM F30339 (see description) molars. This is not to suggest that these species confirm that overall movement of the lower jaw on are directly ancestral to one another. However, this the working side during the power stroke in N. boo- sequence does present, on a simplistic level, a djamullensis was anteromedial. In contrast to working hypothesis that can be tested as additional hypselodont wombats with the exception of War- vombatid specimens come to light. endja, the topography of the worn occlusal surface If we tentatively accept the above model, N. is not flat but dips steeply between the leading boodjamullensis has already advanced from the edge and the centre of the occlusal surface in ante- plesiomorphic state (represented by non-vombatid rior and posterior view. The presence of high- vombatiform marsupials) in that trailing edge angled wear facets on the trailing edge of the enamel is thicker than leading edge enamel and is molars (Figure 4.3) suggest intimate contact more extensive, extending further down and across between leading and trailing edges of molars in the the trailing surface. In contrast, the leading edge opposing jaw in a plane that is at a sharp angle to enamel is relatively thin and restricted and forms the top of the trailing edge enamel. Together these two broad inflections in enamel height: one on the observations suggest that the power stroke in N. anterior moiety and one on the posterior moiety. boodjamullensis consisted of two phases: an initial Enamel height and thickness is least at the con- dorsal (orthal) movement (accounting for the

21 BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH angled wear facets and the steeply dipping occlu- the leading enamel (and anterior dentition). Hence, sal surface on the leading side) followed by a pre- in addition to a shift from a two-phase power stroke dominantly transverse movement of the jaw (the to a one-phase power stroke, there may have been flatter trailing side). Together, these are superim- a shift between shearing being accomplished in posed on the overall anteromedial movement of phase I to it occurring at the end of phase II. The the jaw during the power stroke (Figure 8). hypothesis presented here applies primarily to A two phase power stroke is seen in macropo- teeth that show moderate to advanced wear (in dids (Sanson, 1980; Crompton et al., 2008a) and order to be comparable with hypselodont wombat Phascolarctos cinereus (Crompton et al, 2010), teeth) and would need to be tested using methods although these are not equivalent to phases I and II such as microwear analysis. The bunodont mor- of placental mammals (Crompton et al., 2008a, phology of mildly worn teeth of N. boodjamullensis 2010). In both macropodids and P. cinereus, there suggests that crushing and grinding actions may is an initial orthal component to the power stroke have been of greater importance than in more worn (phase I), followed by a predominantly transverse teeth. movement of the lower jaw (phase II). These observations fit the hypothesis that a two-phase CONCLUSIONS power stroke was symplesiomorphic for Diprot- Nimbavombatus boodjamullensis is a rare, odontia and Vombatiformes and that the special- plesiomorphic wombat with a molar cusp morphol- ised dental adaptations seen by the various ogy that differs from extant wombats in the poor vombatiform families were accompanied by modifi- development of stylar and accessory cusps and cations of this two-phase power stroke, with vom- ridges. It is contemporaneous with the only other batids elaborating phase II. Elaboration of phase II wombat known from deposits older than 10 Ma, and eventual suppression of phase I in hypsel- Rhizophascolonus crowcrofti. Although both taxa odont vombatids, is likely to be associated with are found in fossil deposits of the Riversleigh World loss of the leading edge enamel on the molars. Area in northwestern Queensland, they are not The presence of an orthal component to the found in the same deposits (refer to Travouillon et power stroke is consistent with the skull and jaw al., 2006 for an overview of the Oligo-Miocene architecture of N. boodjamullensis as well as W. deposits in the Riversleigh World Heritage Area). wakefieldi (the only other plesiomorphic wombat They differ in details of the cheek tooth enamel and for which we have cranial remains). The skull of W. in overall size, with N. boodjamullensis being sig- wakefieldi is high and narrow with a weak sagittal nificantly smaller than R. crowcrofti. Hence, crest and is unlike the broad flat cranium of modern although both taxa are rare components of a rain- wombats (Pledge, 1992). The masseteric and pter- forest environment, they almost certainly occupied ygoid fossae of the mandible are both relatively different niches. A phylogenetic analysis confirmed shallow. The corresponding area on the skull for that N. boodjamullensis is a member of a mono- insertion of the masseter is relatively small in both phyletic Vombatidae, but grouped N. boodjamul- W. wakefieldi and N. boodjamullensis in compari- lensis and R. crowcrofti together as a sister group son to modern wombats. The angle of the ascend- to the hypselodont wombats. This sister relation- ing ramus of the mandible is shallower than in ship was based on a single dental character state modern vombatids. These features are indicative shared by N. boodjamullensis and R. crowcrofti. of a relatively greater importance of the temporalis Inflections in enamel height on the molars of N. muscle in mastication compared to modern vom- boodjamullensis and R. crowcrofti can be cor- batids, as was first suggested by Hope and Wilkin- related with the pattern of enamel and dentine son (1982) for W. wakefieldi. tracts seen on the molars of hypselodont wombats, The trailing edge enamel on the molars of N. particularly species of Warendja. It is concluded boodjamullensis and Warendja probably differed in that increasing emphasis on the trailing edge function to that of modern wombats. In modern enamel / second phase of the power stroke in wombats, the trailing edge enamel is much thinner wombats drove many of the obvious dental shape and forms angled and sharp shearing crests. In changes from the early to mid-Miocene to the pres- contrast, the trailing edge enamel on the molars of ent day. the Warendja and N. boodjamullensis is relatively thick and poorly curved and probably functioned in ACKNOWLEDGEMENTS more of a grinding capacity. In N. boodjamullensis, it is possible that shearing was accomplished by Support for research at Riversleigh has come from the Australian Research Council (LP0989969,

22 PALAEO-ELECTRONICA.ORG

FIGURE 8. Jaw movement during the power stroke in Nimbavombatus boodjamullensis. 1, Evidence of jaw move- ment on the surface of the cheek teeth. 2, Movement of the lower jaw during Phase I (left) and Phase II (right) of the power stroke.

23 BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH

LP100200486, DP1094569 and DP130100197 Arena, D.A. 2004. The geological history and develop- grants to M. Archer, S.J. Hand and K.H. Black at ment of the terrain at the Riversleigh World Heritage the University of New South Wales); XSTRATA Area during the middle tertiary. Unpublished PhD Community Partnership Program (North Thesis, University of New South Wales, Sydney, Aus- Queensland); the University of New South Wales; tralia. Beck, R.M.D. 2008. A dated phylogeny of marsupials P. Creaser and the CREATE Fund; the Queensland using a molecular supermatrix and multiple fossil Parks and Wildlife Service; Environment Australia; constraints. Journal of Mammalogy, 89:175-189. the Queensland Museum; the Riversleigh Society, Black, K. 2007. Maradidae: a new family of vombatomor- Inc.; Outback at Isa; Mount Isa City Council; and phian marsupial from the late Oligocene of River- private supporters including K. and M. Pettit, E. sleigh, northwestern Queensland. Alcheringa, Clark, M. Beavis and M. Dickson. Assistance in the 31(1):17-32. field has come from many hundreds of volunteers Black, K. and Archer, M. 1997. Nimiokoala gen. nov. as well as staff and postgraduate students of the (Marsupialia, Phascolarctidae) from Riversleigh, University of New South Wales. Support for this northwestern Queensland, with a revision of Litoko- project has come from a Sylvester Bradley Award ala. Memoirs of the Queensland Museum, 41:209- (to P. Brewer) from the Palaeontological Associa- 228. Black, K.H., Archer, M., and Hand, S.J. 2012. New Ter- tion. Many thanks to J. Louys and A.W. Crompton tiary koala (Marsupialia, Phascolarctidae) from River- who reviewed earlier drafts of this manuscript, to sleigh, Australia, with a revision of phascolarctid K.H. Black for her assistance with the phylogenetic phylogenetics, paleoecology, and paleobiodiversity. analysis and J.J. Hooker for useful discussions. Journal of Vertebrate Paleontology, 32:125-138. Black, K.H., Archer, M., Hand, S.J., and Godthelp, H. REFERENCES 2013. Revision in the diprotodontid marsupial genus Neohelos: systematics and biostratigraphy. Acta Andrews, P., Lord, J.M., and Nesbit Evans, E.M. 1979. Palaeontologica Polonica, 58(4):679-706. Patterns of ecological diversity in fossil and mamma- Brewer, P. 2007. New record of Warendja wakefieldi lian faunas. Biological Journal of the Linnean Society, (Vombatidae; Marsupialia) from Wombeyan Caves, 11:177-205. New South Wales. Alcheringa, 31:153-171. Aplin, K.P. and Archer, M. 1987. Recent advances in Brewer, P., Archer, M., and Hand, S. 2008. Additional marsupial systematics with a new syncretic classifi- specimens of the oldest wombat Rhizophascolonus cation, p. xv-lxxii. In Archer, M. (ed.), Possums and crowcrofti (Vombatidae; Marsupialia) from the Wipa- Opossums: Studies in Evolution. Surrey Beatty & jiri Formation, South Australia: an intermediate mor- Sons Pty Limited, Chipping Norton, England. phology? 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Crompton, A.W., Lieberman, D.E., Owerkowicz, T., Horovitz, I., and Sánchez-Villagra, M.R. 2003. A morpho- Baudinette, R.V., and Skinner, J. 2008b. Motor con- logical analysis of marsupial mammal higher-level trol of masticatory movements in the Southern hairy- phylogenetic relationships. Cladistics, 19:181-212. nosed wombat (Lasiorhinus latifrons), p. 83-111. In Koenigswald, W.v., Sander, P.M., Leite, M.B., Mors, T., Vinyard, C.J., Ravosa, M.J., Wall, C.E. (eds.), Pri- and Santel, W. 1994. Functional symmetries in the mate Craniofacial Function and Biology. Springer, schmelzmuster and morphology of rootless rodent New York. molars. Zoological Journal of the Linnean Society, Crompton, A.W., Barnet, J., Lieberman, D.E., Owerko- 110:141-179. wicz, T., Skinner, J., and Baudinette, R.V. 2008a. Louys, J. 2004. 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Phylogenetic relationships of the families of marsupi- Electron microscopic investigation relating the occlu- als, p. 433–502. In Genoways, H.H. (ed.), Current sal morphology to the underlying enamel structure of Mammalogy. Plenum Press, New York. molar teeth of the wombat (Vombatus ursinus). Jour- Merrilees, D. 1967. Cranial and mandibular characters of nal of Morphology, 200:141-149. modern mainland wombats (Marsupialia, Vombati- Flannery, T.F. and Pledge, N.S. 1987. Specimens of dae) from a palaeontological viewpoint, and their Warendja wakefieldi (Vombatidae: Marsupialia) from bearing on the fossils called Phascolomys parvus by the Pleistocene of South Australia, p. 365-368. In Owen (1872). Records of the South Australian Archer, M. (ed.), Possums and Opossums: Studies in Museum, 15:398-418. Evolution. Surrey Beatty & Sons Pty Limited, Chip- Mones, A. 1982. An equivocal nomenclature: what ping Norton, England. means hypsodonty? Paläontologische Zeitschrift, Flower, W.H. 1867. On the Development and Succes- 56:107-111. sion of the Teeth in the Marsupialia. Philosophical Munson, C.J. 1992. Postcranial descriptions of Ilaria and Transactions of the Royal Society of London, Ngapakaldia (Vombatiformes, Marsupialia) and the 157:631-641. phylogeny of the vombatiforms based on postcranial Frewein, J., Habel, R.E., and Sack, W.O. 1994. Nomina morphology. University of California Publications in Anatomica Veterinaria. World Association of Veteri- Zoology, 125. University of California Press, Berke- nary Anatomists, Ithaca, New York. ley, California. Greaves, W.S. 1973. The inference of jaw motion from Murray, P. 1986. Propalorchestes novaculacephalus wear facets. Journal of Paleontology, 47:1000-1001. gen. et sp. nov., a new palorchestid (Diprotodon- Hernández Fernández, M., Alberdi, M.T., Azanza, B., toidea: Marsupialia) from the middle Miocene Cam- Montoya, P., Morales, J., Nieto, M., and Peláez-Cam- field Beds, Northern Territory, Australia. The Beagle, pomanes, P. 2006. Identification problems of arid Records of the Northern Territory Museum of Arts environments in the Neogene-Quaternary mammal and Sciences, 3:195-211. record of Spain. Journal of Arid Environments, Murray, P.F. 1998. Palaeontology and palaeobiology of 66:585-608. wombats, p. 1-33. In Wells, R.T. and Pridmore, P.A. Hope, J.H.W. and Wilkinson, H.E. 1982. Warendja wake- (eds.), Wombats. Gaughwin & J. Ferris, Surrey fieldi, a new genus of wombat (Maruspialia, Vombati- Beatty & Sons, in association with The Royal Zoolog- dae) from Pleistocene sediments in McEacherns ical Society of South Australia Inc., Chipping Norton. Cave, western Victoria. Memoirs of the National Museum of Victoria, 43:109-121.

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Myers, T. and Archer, M. 1997. Kuterintja ngama (Marsu- Stirton, R.A., Tedford, R.H., and Woodburne, M.O. 1967. pialia, Ilariidae): a revised systematic analysis based A new Tertiary formation and fauna from the Tirari on material from the late Oligocene of Riversleigh, Desert, South Australia. Records of the South Aus- northwestern Queensland. Memoirs of the tralian Museum, 15:427-461. Queensland Museum, 41(2)379-392. Swofford, D.L. 2002. PAUP*. Phylogenetic Analysis Myers, T., Crosby, K., Archer, M., and Tyler, M. 2001. Using Parimony (*and other methods). Sinauer Asso- The Encore Local Fauna, a Late Miocene assem- ciates, Sunderland, Massachusetts. blage from Riversleigh, northwestern Queensland. Tedford, R.H. 2002. The basicranium of the giant wom- Memoir of the Association of Australasian Palaeon- bat Phascolonus gigas Owen (Vombatidae: Marsu- tologists, 25:147-154. pialia) and its significance in phylogeny, p. 39-47. In Owen, R. 1866. Comparative Anatomy and Physiology Emery, R.J. (ed.), Cenozoic Mammals of Land and of Vertebrates. Longmans Green, London. Sea: Tributes to the Career of Clayton E. Ray. Smith- Pledge, N.S. 1992. The weird wonderful wombat War- sonian Institution Press. endja wakefieldi Hope & Wilkinson. The Beagle, Travouillon, K.J., Archer, M., Hand, S.J., and Godthelp, Records of the Northern Territory Museum of Arts H. 2006. Multivariate analyses of Cenozoic mamma- and Sciences, 9:111-114. lian faunas from Riversleigh, northwestern Reig, O.A., Kirsch, J.A.W., and Marshall, L.G. 1987. Sys- Queensland. Alcheringa Special Issue, 1:323-349. tematic relationships of the living and the neoceno- Travouillon, K.J., Gurovich, Y., Beck, R.M.D., and Muir- zoic American “opossum-like” marsupials (Suborder head, J. 2010. An exceptionally well-preserved short- Didelphimorphia), with comments on the classifica- snouted bandicoot (Marsupialia: Peramelemorphia) tion of these and of the Cretaceous and Paleogene from Riversleigh’s Oligo-Miocene deposits, north- New World and European metatherians, p. 1-89. In western Queensland, Australia. Journal of Vertebrate Archer, M. (ed.), Possums and Opossums: Studies in Paleontology, 30:5, 1528-1546. Evolution. Surrey Beatty and Sons Pty. Ltd., Chipping Tummers, M. and Thesleff, I. 2003. Root or crown: a Norton, New South Wales. developmental choice orchestrated by the differential Rensberger, J.M. 1971. Entoptychine pocket regulation of the epithelial stem cell niche in the tooth gophers(Mammalia, Geomyoidea) of the Early Mio- of two rodent species. Development, 130:1049-1057. cene John Day Formation, Oregon. University of Cal- Weisbecker, V. and Archer, M. 2008. Parallel evolution of ifornia Publications in Geological Sciences, 90:1-163. hand anatomy in kangaroos and vombatiform marsu- Rensberger, J.M. 1973. An occlusion model for mastica- pials: functional and evolutionary implications. Palae- tion and dental wear in herbivorous mammals. Jour- ontology, 51(2):321-338. nal of Paleontology, 47:515-528. Weisbecker, V. and Sánchez-Villagra, M.R. 2006. Carpal Rensberger, J.M. 1975. Function in the cheek tooth evo- evolution in diprotodontian marsupials. Zoological lution of some hypsodont geomyid rodents. Journal Journal of the Linnean Society, 146:369-384. of Paleontology, 49:10-22. Woodburne, M.O. 1984. Families of marsupials: relation- Rougier, G.W., Wible, J.R., and Novacek, M.J. 1998. ships, evolution and biogeography, p. 48-71. In Implications of Deltatheridium specimens for early Broadhead, T.W. (ed.), Mammals: Notes for a Short marsupial history. Nature, 396:459-463. Course, Studies in Geology (Vol. 8). University of Sánchez-Villagra, M.R. and Wible, J.R. 2002. Patterns of Tennessee, Knoxsville. evolutionary transformation in the petrosal bone and Woodburne, M.O., Tedford, R.H., Archer, M., and some basicranial features in marsupial mammals, Pledge, N.S. 1987. Madakoala, a new genus and two with special reference to didelphids. Journal of Zoo- species of Miocene koalas (Marsupialia: Phascolarc- logical Systematics and Evolutionary Research, tidae) from South Australia and a new species of 40:26-45. Perikoala, p. 293-317. In Archer, M. (ed.), Possums Sanson, G.D. 1980. The morphology and occlusion of and Opossums: Studies in Evolution. Surrey Beatty the molariform cheek teeth in some Macropodinae and Sons Pty. Ltd., Chipping Norton, New South (Marsupialia: Macropodidae). Australian Journal of Wales. Zoology, 28:341-365. 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APPENDIX 1.

List of characters used in the phylogenetic analysis. Characters indicated by an asterisk are ordered in the analysis. Absent; (1) Moderate enamel tracts / changes in enamel height around the 1.* Number of upper incisors (modified from tooth; (2) Extensive enamel tracts / Springer et al., 1997, Rougier et al., 1998, changes in enamel height around the Wroe et al., 2000, Horovitz and Sánchez- tooth. Villagra, 2003 and Black et al., 2012): (0) More than three; (1) Two or Three; (2) 12. Anteriorly concave lower / anteriorly con- One. vex upper molar lophs (Black et al., 2012): (0) Absent; (1) Present. 2. Size of I1 relative to I2 (Black et al., 2012): 1 (0) Equal or similar in length; (1) Large, 13. M with decrease in enamel height on lin- elongate. gual surface at constriction or just posterior to this: (0) Absent; (1) Present. 3. Upper canine (modified from Springer et al., 1997, Horovitz and Sánchez-Villagra, 14.* Parastyle development on M1 (Black and 2003 by Black et al., 2012): (0) Present; (1) Archer, 1997; Black et al., 2012): (0) Absent or vestigal. Absent/small; (1) Moderately developed expansion of anterobuccal tooth corner; 4.* Number of upper premolars (Black et al., (2) Large, cuspate and pyramidal. 2012): (0) Three; (1) Two; (2) One. 15. Presence of a cusp on posterobuccal side 5. Posterobuccal cusp on P3 (Woodburne et of M1 (and occasionally M2) in position of al., 1987; Black and Archer, 1997; Myers St-E: (0) Absent; (1) Present. and Archer, 1997; Black et al., 2012): (0) Absent; (1) Present. 16.* St-C larger and better developed than St-B 2 6. Enamel extending down the buccal sur- on M : (0) Absent; (1) Similar in size; (2) Present. face of P3 and onto the root: (0) Absent; (1) Present. 17. Presence of crest connecting paracone to St-B on M2: (0) Absent; (1) Present. 7.* Size of P3 relative to M1 (modified from Black and Archer, 1997 and Black et al., 18.* Separation of stylar cusps C and D (modi- 2012): (0) P3 length greater than M1 fied from Myers and Archer, 1997 and length; (1) P3 length less than or equal to Black et al., 2012): (0) Close together; (1) Separated; (2) Separated by a large M1 length; (2) P3 length less than or equal trough. to 80% of M1 length. 19. Postprotocrista (Archer, 1984; Black et al., 8.* Molar morphology (Black et al., 2012): (0) 2012): (0) Present; (1) Absent. Tribosphenic; (1) Selenodont; (2) Semi- lophodont/bunodont; (3) Lophodont but 20. M2 width of anterior moiety versus tooth stylar cusps still evident on lophs; (4) Fully length (modified from Springer et al., 1997; lophodont. Horovitz and Sánchez-Villagra, 2003 by 2 9. Hypselodont cheek teeth (modified from Black et al., 2012): (0) M longer than 2 Murray, 1998; Black et al., 2012): (0) wide; (1) M width is greater or equal to Absent; (1) Present. length. 10. Enamel noticeably thicker on trailing edge 21. M4 metaconule (Black et al., 2012): (0) (lingual surface on upper molars and buc- Absent / significantly reduced and cal surface on lower molars) relative to retracted towards posterior cingulum; (1) leading edge of molars (buccal surface on Distinct / cuspate. upper molars and lingual surface on lower 22. Posteriorly increasing (upper) molar gradi- molars): (0) Absent; (1) Present. ent (modified from Black, 2007 and Black 11.* Presence of enamel tracts that extends et al., 2012): (0) Absent, M4 / M1 is less down the lingual surface of upper molars than or equal to 1; (1) Present, M4 / M1 is and buccal surface of lower molars: (0) greater than 1.

28 PALAEO-ELECTRONICA.ORG

23.* Number of lower incisors (modified from premaxillary-maxillary suture to a position Springer et al., 1997, Rougier et al., 1998, just anterior to the cheek tooth. Wroe et al., 2000, Luo et al., 2002, Horo- 33. Lateral edge of palate emarginated from I1 vitz and Sánchez-Villagra, 2003 and Black to P3 in ventral view (modified from Ted- et al., 2012): (0) Two or more; (1) One. ford, 2002): (0) Absent; (1) Present. 24. Inclination angle of I (Marshall et al., 1 34. Palate width opposite first molar (ventral 1990; Springer et al., 1997; Horovitz and view) (Merrilees, 1967; Scott et al., 1988): Sánchez-Villagra, 2003; Black, 2007; (0) Narrow, less than buccolingual width of Black et al., 2012): (0) High (greater or M1; (1) Wide, equal to or greater than buc- equal to 30 degrees); (1) Low (less than 30 colingual width of M1. degrees). 35. Median premaxillary process (Tedford, 25. Development of paraconid and paracristid 2002): (0) Absent; (1) Well-developed or on M (modified from Myers and Archer, 1 present as a low spine at the midline dor- 1997, Horovitz and Sánchez-Villagra, 2003 sal surface of the premaxilla. by Black, 2007; Black et al., 2012): (0) 36.* Position of infraorbital foramen: (0) Close Paraconid present and paracristid well- to level of alveolar process; (1) Approxi- developed; (1) Paraconid weak or absent; mately midway between dorsal surface of paracristid present and distinct; (2) skull and alveolar process; (2) Closer to Paraconid and paracristid absent. dorsal surface of skull than alveolar pro- 26. Protostylid on M1 (Woodburne et al. 1987; cess of tooth row. Black and Archer 1997; Myers and Archer 37.* Posterior palatal vacuities (maxillopalatine 1997; Springer et al. 1997; Black 2007): (0) vacuity) (modified from Archer, 1984, Reig Absent; (1) Present. et al., 1987, Rougier et al., 1998, Wroe et 27. Cristid obliqua (modified from Black, 2007 al., 2000, Horovitz and Sánchez-Villagra, and Black et al., 2012): (0) Well-devel- 2003 and Black et al., 2012): (0) Extends oped, meets or approaches postprotocris- anteriorly to a point anterior of M3; (1) Con- tid lingual to horizontal tooth midline; (1) fined within palate, opposite M3-4; (2) Well-developed, meets or approaches Absent. postprotocristid buccal to horizontal tooth midline; (2) Weak / absent. 38.* Nasal aperture retracted beyond incisor arcade (modified from Black et al., 2012): 28. Distinct and separate paraconid on M2-4: (0) Absent or just posterior to incisor (0) Absent; (1) Present. arcade; (1) Retracted to above diastema 29. Paraconid located on lingual side of tooth (or level of premaxillary-maxillary suture); on M2-3 (or preprotocristid / paracristid ter- (2) Retracted to above cheek tooth row. minates on lingual side of tooth): (0) Pres- 39. Nasomaxillary suture length relative to ent; (1) Absent, located close to midline or nasopremaxillary suture length (dorsal buccal side of tooth. view) (Scott et al., 1988): (0) Nearly same 30. Paraconid connected to protoconid via or greater; (1) Far less than nasopremaxil- lary suture length. crest on M2-3 (or well-developed preproto- cristid / paracristid): (0) Present; (1) 40. Separate left and right parietal ridges along Absent. entire length of parietal bone: (0) Absent; 31. Presence of a crest connecting entoconid (1) Present. and hypoconid: (0) Absent; (1) Present. 41.* Masseteric process (Wroe et al., 1998; 32. Incisive foramen posterior (modified from modified version in Black et al., 2012): (0) Dawson, 1983b; Murray, 1998; Tedford, Absent; (1) Short; (2) Elongate. 2002): (0) Absent; (1) Present, the incisive 42. Dorsoventral position of ventral extent of foramina lie posteriorly, just anterior to P3, anterior zygomatic root (relative to the in a deep pocket at the rear of the dias- cheek tooth row): (0) Close to level of alve- tema. The posterior position of the foram- olar process; (1) Distant to alveolar pro- ina correspondingly displaces the cess.

29 BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH

43. Anteroposterior position of ventral extent 56. Narrow mastoid strip on occiput (Murray, of anterior zygomatic root (relative to the 1986; Black et al., 2012): (0) Absent; (1) cheek tooth row): (0) Above M3 or M4; (1) Present. Above junction between M2 and M3; (2) 57. Ventrolaterally flared mastoid process on Above M2; (3) At junction between M1 and occiput (Murray 1986; Black et al., 2012): M2 or anterior to M2. (0) Absent; (1) Present. 44. Infraorbital shelf (Black et al., 2012): (0) 58.* Length of articular surface (mandible) rela- Well-developed; (1) Weak. tive to length of cheek tooth row (modified 45. Postglenoid process (Springer et al., 1997; from Scott et al., 1988): (0) Short, ratio of Horovitz and Sánchez-Villagra, 2003; 0.4 or less; (1) Medium, ratio of 0.5 to 0.6; modified version in Black et al., 2012): (0) (2) Long, ratio of 0.7 or greater. Present; (1) Absent. 59.* Forward extent of ectalveolar groove of 46. Tympanic cavity roof elements (modified mandible (Dawson, 1983a): (0) Posterior from Travoullion et al., 2010 and Black et of M4; (1) Junction between M3 and M4 to al., 2012): (0) Alisphenoid (no squamosal mid M4; (2) Adjacent to M3. contribution); (1) Alisphenoid and squamo- 60.* Depth of masseteric fossa (mandible) sal; (2) Squamosal (no alisphenoid contri- (Merrilees, 1967; Scott et al., 1988): (0) bution). Shallow to medium; (1) Deep; (2) Very 47. Tympanic floor elements (Black et al., deep. 2012): (0) Alisphenoid; (1) Alisphenoid and 61. Angle of the anterior border of the ascend- squamosal; (2) Squamosal. ing ramus (mandible) (modified from Hope 48.* Alisphenoid tympanic wing (modified from and Wilkinson, 1982; Black, 2007; Black et Springer et al., 1997, Wroe et al., 1998, al., 2012): (0) < 70°; (1) > or = 70°. Horovitz and Sánchez-Villagra, 2003 and 62.* Posterior extent of mandibular symphysis Black et al., 2012): (0) Absent; (1) Short; (mandible) (Black, 2007; Black et al., (2) Moderate to elongate, extends under 2012): (0) Anterior to P3; (1) Below P3; (2) periotic. Below M1; (3) Below M2-3. 49. Epitympanic fenestra developed in post- 63.* Diastema length between I and P (modi- glenoid cavity (Black et al., 2012): (0) 1 3 Absent; (1) Present. fied from Black, 2007 and Black et al., 2012): (0) < 30% horizontal ramus length; 50. Non-auditory sinuses (Murray, 1986; Black (1) Approximately 30% horizontal ramus et al., 2012): (0) Absent; (1) Present. length; (2) > 30% horizontal ramus length. 51. Posterior epitympanic fossa (modified from 64. Distance between anterior edge of P and Murray, 1986; modified from Black et al., 3 posterior edge of M relative to length of 2012): (0) Absent / weak; (1) Moderate to 4 deep. horizontal ramus (mandible) (Black et al., 2012): (0) > 60%; (1) < or = 60%. 52.* Postglenoid cavity / epitympanic fossa (modified from Murray, 1998, Tedford, 65. Flared masseteric eminences (mandible) 2002, Louys, 2004 and Black et al., 2012): (Murray, 1998; Black et al., 2012): (0) (0) Absent; (1) Present, but shallow; (2) Absent / weak; (1) Moderately to strongly Present and moderately extensive / deep. flared. 53.* Rostral tympanic process of periotic (Rou- 66. Masseteric foramen (Black, 2007; Black et gier et al., 1998; Sánchez -Villagra and al., 2012): (0) Absent; (1) Present. Wible, 2002; Horovitz and Sánchez-Villa- 67. Fused mandibular symphysis: (0) Absent; gra, 2003 modified version; Black et al., (1) Present. 2012): (0) Strong; (1) Weak / absent. 68. Cervical vertebrae: combined length of C3- 54. Posterior parietal width (Black et al., 2012): C7 divided by width of C7 (Munson, 1992): (0) Broad; (1) Narrow. (0) > 1.0 (long neck); (1) < 1.0 (short neck). 55. Interparietal (Louys et al., 2009; Black et 69. Humerus: max. width across distal end al., 2012): (0) Present; (1) Absent. divided by length (Munson, 1992): (0) < or = 0.3; (1) > 0.3.

30 PALAEO-ELECTRONICA.ORG

70. Humerus: deltoid ridge (Munson, 1992): Villagra, 2006 and Weisbecker and Archer, (0) Has no lateral overhang, or a very 2008): (0) Large, hooked and curves medi- minor one; (1) Has a large flaring over- ally; (1) Reduced, not as hooked and does hang. not curve as far medially. 71.* Humerus: deltoid tuberosity (modified from 85.* MC I: max. width divided by length (modi- Scott and Richardson, 1988): (0) Angle fied from Munson, 1992 by Weisbecker between deltoid and pectoral crests < 30°; and Archer, 2008): (0) < 0.4 ; (1) 0.4 to 0.5; (1) Angle between 30° and 40°; (2) Angle > (2) > 0.5. 40°. 86. MC II: proximal end (Munson, 1992; Weis- 72. Ulna: anteroposterior thickness at semilu- becker and Archer, 2008): (0) Mediolater- nar notch divided by bone length (modified ally compressed; (1) Expanded and from Munson, 1992): (0) < or = 0.10; (1) > concave. 0.10. 87. MC III: facet for MC IV (modified from Mun- 73. Ulna: length of olecranon process divided son, 1992): (0) Proximal only to ligament by bone length (Munson, 1992): (0) < 0.20; pit (no dorsal component); (1) Dorsal to lig- (1) > or = 0.20. ament pit (no proximal component); (2) 74. Ulna: max. anteroposterior thickness at Dorsal and proximal to ligament pit. coronoid process divided by bone length 88. MC III: facet for MC IV (modified from Mun- (Munson, 1992): (0) < 0.2; (1) > or = 0.2. son, 1992 by Weisbecker and Archer, 75. Radius: length (Munson, 1992): (0) > 2008): (0) Facing laterally or only slightly length of humerus; (1) < or = length of distally slanted; (1) Strongly distally slanted humerus. or completely facing distally. 76. Radius: anteroposterior thickness of distal 89. MC III: magnum facet (modified from Mun- end divided by bone length (Munson, son 1992): (0) Grooved or concave; (1) 1992): (0) < or = 0.1; (1) > 0.1. Convex or flat to slightly convex. 77. Cuneiform: position relative to scapholunar 90. MC III: MC II facet (Munson, 1992; Weis- (Munson, 1992; Weisbecker and Archer, becker and Archer, 2008): (0) Separate, 2008): (0) Directly lateral to scapholunar; distinct, and lateral to the magnum facet; (1) More proximal than the scapholunar. (1) Continuous with the magnum facet. 78. Cuneiform: ridge between ulnar and pisi- 91.* MC V: max. width of distal end divided by form facets (Weisbecker and Archer, length (modified from Munson, 1992 and 2008): (0) Middle section sinks below the Weisbecker and Archer, 2008): (0) < 0.4; rim of the cuneiform; (1) High rising (1) 0.4 to 0.5; (2) > 0.5. throughout, straight. 92.* Proximal phalanges II to V of manus, IV 79. Pisiform: area of ulnar facet (Munson, and V only in pes: mid-shaft width divided 1992; Weisbecker and Archer, 2008): (0) < by length (modified from Munson, 1992 area of cuneiform facet; (1) > or = area of and Weisbecker and Archer, 2008): (0) < cuneiform facet. 0.3; (1) 0.3 to 0.4; (2) > 0.4. 80. Pisiform: width divided by thickness (Mun- 93. Proximal phalanges, manus or pes: distal son, 1992): (0) < 0.5; (1) > or = 0.5. ends (Munson, 1992; Weisbecker and Archer, 2008): (0) Not tapered; (1) Dorso- 81. Scaphoid: distal surface (Weisbecker and ventrally tapered, so that the articulation Archer, 2008): (0) Single facet, smooth; (1) for the medial phalanx faces ventrally. Separated into two distinct facets. 94.* Medial phalanx III of manus or IV of pes: 82. Scaphoid: distolateral process (Weis- length divided by length of corresponding becker and Sánchez-Villagra, 2006): (0) metapodial (modified from Munson, 1992 Absent; (1) Present. and Weisbecker and Archer, 2008): (0) < 83. Unciform: area of MC V facet (Munson, 0.30; (1) 0.30 to 0.40; (2) > 0.40. 1992; Weisbecker and Archer, 2008): (0) < 95. Pelvis: dorsoventral height at symphysis MC IV facet; (1) > or = area of MC IV facet. divided by width at mid-ischium (Munson, 84. Unciform: hamate process (modified from 1992): (0) < 0.8; (1) > or = 0.8. Munson, 1992, Weisbecker and Sánchez-

31 BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH

96. Pelvis: ilium (Munson, 1992): (0) Only 106. Cuboid (Munson, 1992): (0) No contact; (1) slightly dorsoventrally flattened, or medio- Contacts astragalus. laterally flattened; (1) Greatly dorsoven- 107. Cuboid: area of MT V facet (Munson, trally flattened. 1992): (0) < MT IV facet; (1) > or = area of 97.* Pelvis: width of iliac crest divided by length MT IV facet. of ilium (Munson, 1992): (0) < 0.30; (1) 108. Ectocuneiform: length divided by height 0.30 to 0.50; (2) > 0.50. (Munson, 1992): (0) > or = 0.8; (1) < 0.8. 98. Epipubics: width at mid-bone divided by 109. Entocuneiform: MT I facet (Munson, 1992): length X 100 (Munson, 1992): (0) < 10; (1) (0) Saddle-shaped (concavo-convex); (1) > or = 10. Convex. 99. Femur: width of proximal end divided by 110. Entocuneiform: navicular facet (Munson, length (Munson, 1992): (0) < 0.3; (1) > or = 1992): (0) Shorter than or equal to meso- 0.3. cuneiform facet; (1) Longer than mesocu- 100. Tibia: length (Munson, 1992): (0) > or = neiform facet. length of femur; (1) < length of femur. 111. Metatarsal I: entocuneiform facet (Munson, 101. Fibula: lateral notch on distal end (Mun- 1992): (0) Mostly convex; (1) Strong con- son, 1992): (0) Clearly present; (1) cave component. Extremely slight or absent. 112. MT II and III: mid-shaft width divided by 102. Fibula: width of proximal end divided by bone length (Munson, 1992): (0) < 0.15 ; bone length (modified from Munson, (1) > or = 0.15. 1992): (0) < 0.10; (1) > or = 0.10. 113. MT IV: proximal end (Munson, 1992): (0) 103. Fibula: femoral facet (Munson, 1992): (0) Square; (1) Mediolaterally tapered. Not present; (1) Present. 114. MT V versus MT III (modified from Mun- 104. Astragalus: lateral tibial facet (modified son, 1992): (0) MT III longer that MT V; (1) from Munson, 1992): (0) Mostly convex; MT V longer than MT III. (1) Mostly concave. 115.* MT V: max. width divided by length (modi- 105. Astragalus: head (modified from Munson, fied from Munson, 1992): (0) < 0.50; (1) 1992): (0) Wider than long; (1) Narrow, 0.50 to 0.70; (2) > 0.70. mediolaterally compressed, or length and width are equal.

32 PALAEO-ELECTRONICA.ORG

APPENDIX 2.

Data matrix used for phylogenetic analysis. ? indicates missing data; - indicates inapplicable character; polymorphic states indicated by both states in brackets, e.g., (01).

Didelphis marsupialis 0000100000 0-01120201 0000001100 0001000000 000?000200 00?0010000 10-1000000 0????????? ?????????? ????00000? ?????????? ????? Perameles bougainville 0000?01000 0-020??101 0000002100 000100000- 001?0???00 ???0???000 00-1??0000 0010000000 0101002000 0000101000 0000100000 00010 Galadi speciosus 0000002000 0-000??001 000?001100 0001000000 0000000?00 0000100?00 10-1000??? ?????????? ?????????? ????101?0? ?????????? ????? Ngapakaldia tedfordi 1112002400 01001??210 111120201? 10?1012110 1011022011 1211110?00 122101??1? ?10?111111 1010202000 1102???111 1111011000 10111 Ilaria ilumindens 110210210? 0-01121200 11??110??? ???1??1??? 201??????? ????????0? 1?00101??? ?111?0???? ????111111 ?11??????? ?????????? ??1?? Propalorchestes ??12002300 0100121210 11112010?? 1101?12210 2021021?11 121111?210 122111???? novaculocephalus ?????????? ?????????? ?????????? ?????????? ????? Nimiokoala greystanesi 1002102100 0-02101001 0010010010 00?1?0?010 1030?1??00 ??000????0 1300010??? ?????????? ?????????? ?????????? ?????????? ????? Priscileo roskellyae 1100000200 0-011??101 ?0101010?? 0001?00000 ?030011200 ?210100??0 ?10001???? ?????????? ?????????? ?????????? ?????????? ????? Lasiorhinus latifrons 2-12?1?211 20001012(01)0 0011?01001 10111211(01)1 0120122000 1210111121 1311111111 2111101111 10?121?111 2211012111 1111011111 ?1102 Nimbavombatus 1?02012201 1011?????0 00???????? ??01?10??? 0020?????? ?????????? ?????????? boodjamullensis ?????????? ?????????? ?????????? ?????????? ????? Phascolonus gigas 2-12?0??11 2?0??????0 ?011?????? ?1101?12?1 01?01????? ?2?????122 0301111111 2111111111 1?1121?1?1 221?112011 11110????? ????? Rhizophascolonus crowcrofti ???????201 (12)?1??????0 ?????????? ?????????? ?????????? ?????????0 1????????? ?????????? ?????????? ?????????? ?????????? ????? Vombatus ursinus 2-12?1?211 20011012?0 1010?01101 (01)000021111 0120122?00 1110111212 1311111111 1111111111 1001211111 2211012111 1111011111 11102 Warendja wakefieldi 2-12?1??11 2?0??????0 ?010?????? ?001?10??0 00101220?? ?1?01????0 0210110??1 1????????? ?????????? ?????????? ?????????? ????? Muramura williamsi 11020?0200 00?100?201 1011101010 1000?0?1?0 20100????? 01??1?1110 11210?0000 000000???? ?????????? ????????11 0111??0??? ????? Marada arcanum ???????200 00???????? ??11101010 1????????? ?????????? ????????00 0121010??? ?????????? ?????????? ?????????? ?????????? ?????

33 BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH

APPENDIX 3.

Comparative dental measurements.

NODE NODE CHARACTER CHANGE CHARACTER DESCRIPTION (from) (to) NUMBER

1 1 0→1 Number of upper incisors 8 0→1 Molar morphology 23 0→1 Number of lower incisors

28 1→0 Distinct and separate paraconid on M2-4

29 0→1 Paraconid located on lingual side of tooth on M2-3 41 0→1 Masseteric process 43 0→3 Anteroposterior position of ventral extent of anterior zygomatic root (relative to the cheek tooth row)

46 0→1 Tympanic cavity roof elements 62 0→1 Posterior extent of mandibular symphysis (mandible)

66 0→1 Masseteric foramen 12 2 0→1Size of I1 relative to I2 8 1→2 Molar morphology

25 0→1 Development of paraconid and paracristid on M1 53 0→1 Rostral tympanic process of periotic 2 3 18 1→2 Separation of stylar cusps C and D 31 0→1 Presence of a crest connecting entoconid and hypoconid

38 0→1 Nasal aperture retracted beyond incisor arcade 43 3→1 Anteroposterior position of ventral extent of anterior zygomatic root (relative to the cheek tooth row)

63 0→1 Diastema length between I1 and P3 34 7 0→2Size of P3 relative to M1 20 1→0 M2 width of anterior moiety versus tooth length 36 0→1 Position of infraorbital foramen 51 0→1 Posterior epitympanic fossa 62 1→2 Posterior extent of mandibular symphysis (mandible)

69 0→1 Humerus: max. width across distal end divided by length

72 0→1 Ulna: anteroposterior thickness at semilunar notch divided by bone length

75 0→1 Radius: length 101 0→1 Fibula: lateral notch on distal end 107 0→1 Cuboid: area of MT V facet

34 PALAEO-ELECTRONICA.ORG

NODE NODE CHARACTER CHANGE CHARACTER DESCRIPTION (from) (to) NUMBER

4 5 3 0→1 Upper canine 8 2→3 Molar morphology 12 0→1 Anteriorly concave lower / anteriorly convex upper molar lophs

14 1→0 Parastyle development on M1 19 0→1 Postprotocrista

25 1→2 Development of paraconid and paracristid on M1 37 1→2 Posterior palatal vacuities (maxillopalatine vacuity)

44 0→1 Infraorbital shelf 49 0→1 Epitympanic fenestra developed in postglenoid cavity

50 0→1 Non-auditory sinuses 52 1→2 Postglenoid cavity / epitympanic fossa 54 0→1 Posterior parietal width 4 6 86 0→1 MC II: proximal end 87 2→1 MC III: facet for MC IV 88 0→1 MC III: facet for MC IV 89 0→1 MC III: magnum facet 90 0→1 MC III: MC II facet 93 0→1 Proximal phalanges, manus or pes: distal ends

6 7 6 0→1 Enamel extending down the buccal surface of P3 and onto the root

11 0→1 Presence of enamel tracts that extends down the lingual surface of upper molars and buccal surface of lower molars

41 1→0 Masseteric process 7 8 3 0→1 Upper canine 9 0→1 Hypselodont cheek teeth 11 1→2 Presence of enamel tracts that extends down the lingual surface of upper molars and buccal surface of lower molars

8 9 36 1→2 Position of infraorbital foramen 40 0→1 Separate left and right parietal ridges along entire length of parietal bone

42 0→1 Dorsoventral position of ventral extent of anterior zygomatic root (relative to the cheek tooth row)

60 0→1 Depth of masseteric fossa (mandible) 62 2→3 Posterior extent of mandibular symphysis (mandible)

35 BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH

NODE NODE CHARACTER CHANGE CHARACTER DESCRIPTION (from) (to) NUMBER

910330→1Lateral edge of palate emarginated from I1 to P3 in ventral view

35 0→1 Median premaxillary process 52 1→2 Postglenoid cavity / epitympanic fossa 59 1→2 Forward extent of ectalveolar groove of mandible

71 1→2 Humerus: deltoid tuberosity 811130→1M1 with decrease in enamel height on lingual surface at constriction or just posterior to this

36 PALAEO-ELECTRONICA.ORG

APPENDIX 4.

Cusp morphology of P3 to M2 of modern wombats compiled from CT scans of Lasiorhinus latifrons (SAM M4157 and SAM M1924) and Vombatus ursinus (MNV C19028 and MNV C3133). 1, Upper dentition of L. latifrons. 2, Upper dentition of V. ursinus. 3, Lower dentition of L. latifrons. 4, Lower dentition of V. ursinus. Abbreviations as follows: end refers to entoconid, hyd refers to hypoconid, ME refers to metacone, med refers to metaconid, MEL refers to metaconule, PA refers to paracone, PR refers to protocone, prd refers to protoconid.

37 BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH

APPENDIX 5.

List of unambiguous apomorphies. Node numbers correspond to Figure 7.2

NODE NODE CHARACTER CHANGE CHARACTER DESCRIPTION (from) (to) NUMBER

1 1 0→1 Number of upper incisors 8 0→1 Molar morphology 23 0→1 Number of lower incisors

28 1→0 Distinct and separate paraconid on M2-4

29 0→1 Paraconid located on lingual side of tooth on M2-3 41 0→1 Masseteric process 43 0→3 Anteroposterior position of ventral extent of anterior zygomatic root (relative to the cheek tooth row)

46 0→1 Tympanic cavity roof elements 62 0→1 Posterior extent of mandibular symphysis (mandible)

66 0→1 Masseteric foramen 12 2 0→1Size of I1 relative to I2 8 1→2 Molar morphology

25 0→1 Development of paraconid and paracristid on M1 53 0→1 Rostral tympanic process of periotic 2 3 18 1→2 Separation of stylar cusps C and D 31 0→1 Presence of a crest connecting entoconid and hypoconid

38 0→1 Nasal aperture retracted beyond incisor arcade 43 3→1 Anteroposterior position of ventral extent of anterior zygomatic root (relative to the cheek tooth row)

63 0→1 Diastema length between I1 and P3 34 7 0→2Size of P3 relative to M1 20 1→0 M2 width of anterior moiety versus tooth length 36 0→1 Position of infraorbital foramen 51 0→1 Posterior epitympanic fossa 62 1→2 Posterior extent of mandibular symphysis (mandible)

69 0→1 Humerus: max. width across distal end divided by length

72 0→1 Ulna: anteroposterior thickness at semilunar notch divided by bone length

75 0→1 Radius: length 101 0→1 Fibula: lateral notch on distal end 107 0→1 Cuboid: area of MT V facet

38 PALAEO-ELECTRONICA.ORG

NODE NODE CHARACTER CHANGE CHARACTER DESCRIPTION (from) (to) NUMBER

4 5 3 0→1 Upper canine 8 2→3 Molar morphology 12 0→1 Anteriorly concave lower / anteriorly convex upper molar lophs

14 1→0 Parastyle development on M1 19 0→1 Postprotocrista

25 1→2 Development of paraconid and paracristid on M1 37 1→2 Posterior palatal vacuities (maxillopalatine vacuity)

44 0→1 Infraorbital shelf 49 0→1 Epitympanic fenestra developed in postglenoid cavity

50 0→1 Non-auditory sinuses 52 1→2 Postglenoid cavity / epitympanic fossa 54 0→1 Posterior parietal width 4 6 86 0→1 MC II: proximal end 87 2→1 MC III: facet for MC IV 88 0→1 MC III: facet for MC IV 89 0→1 MC III: magnum facet 90 0→1 MC III: MC II facet 93 0→1 Proximal phalanges, manus or pes: distal ends

6 7 6 0→1 Enamel extending down the buccal surface of P3 and onto the root

11 0→1 Presence of enamel tracts that extends down the lingual surface of upper molars and buccal surface of lower molars

41 1→0 Masseteric process 7 8 3 0→1 Upper canine 9 0→1 Hypselodont cheek teeth 11 1→2 Presence of enamel tracts that extends down the lingual surface of upper molars and buccal surface of lower molars

8 9 36 1→2 Position of infraorbital foramen 40 0→1 Separate left and right parietal ridges along entire length of parietal bone

42 0→1 Dorsoventral position of ventral extent of anterior zygomatic root (relative to the cheek tooth row)

60 0→1 Depth of masseteric fossa (mandible) 62 2→3 Posterior extent of mandibular symphysis (mandible)

39 BREWER ET AL.: NEW WOMBAT FROM RIVERSLEIGH

NODE NODE CHARACTER CHANGE CHARACTER DESCRIPTION (from) (to) NUMBER

910330→1Lateral edge of palate emarginated from I1 to P3 in ventral view

35 0→1 Median premaxillary process 52 1→2 Postglenoid cavity / epitympanic fossa 59 1→2 Forward extent of ectalveolar groove of mandible

71 1→2 Humerus: deltoid tuberosity 811130→1M1 with decrease in enamel height on lingual surface at constriction or just posterior to this

40